Introduction to IBM PL/1 Programming Language

Created by Sanjay Sinha
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INTRODUCTION TO PL/1
PL/I is a structured language to develop
systems and applications programs (both
business and scientific).
Significant features :
v Allows Free format
v Regards a program as a continuous stream of data
v Supports subprogram and functions
v Uses defaults

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Building blocks of PL/I :
v Made up of a series of subprograms and called
Procedure
v Program is structured into a MAIN program and
subprograms.
v Subprograms include subroutine and functions.
Every PL/I program consists of :
v At least one Procedure
v Blocks
v Group

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v There must be one and only one MAIN procedure to every
program, the MAIN procedure statement consists of :
v Label
v The statement ‘PROCEDURE OPTIONS (MAIN)’
v A semicolon to mark the end of the statement.
Coding a Program :
1. Comment line(s) begins with /* and ends with */.
Although comments may be embedded within a PL/I
statements , but it is recommended to keep the
embedded comments minimum.

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2. The first PL/I statement in the program is the
PROCEDURE statement :
AVERAGE : PROC[EDURE] OPTIONS(MAIN);
AVERAGE -- it is the name of the
program(label) and compulsory and marks the
beginning of a program.
OPTIONS(MAIN) -- compulsory for main
programs and if not specified , then the
program is a subroutine.
A PL/I program is compiled by PL/I compiler
and converted into the binary , Object program
file for link editing .

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Advantages of PL/I are :
1. Better integration of sets of programs
covering several applications.
2. Easier interchangeability of files
3. Fewer programs to be written in a machine
oriented language.
4. Better machine utilization, greater use of
channels , more flexible storage assignment,
better intercept handling.

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The process of compiling a PL/I program and
executing it in the computer’s memory takes
place through JCL.
Some restrictions :
Col # 1 for O.S.
Col # 2 - 72 for PL/I statements
Col # 73 - 80 ignored by complier
PL/I Language Components :
1. Character sets : 60 characters in total, A - Z ,
extended characters e.g # , @ , $ , 0 -9 and 21
special characters.

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2. Identifiers : Used to name data, procedures , files ,
labels of PL/I statements and keywords.
An identifiers for data names , statement labels and
internal procedure names may be from 1 to 30
alphabetic characters ( A – Z,@, !, #, $ ) , numeric
digits (0-9) and underscore character.
3. Statement format :
LABEL : KEYWORD STATEMENT OPTIONS ;
the source program . A PL/I statement may be
continued across several lines.One line may contain
several statements terminated by semi-colon.
4. PL/I constants : A constant is a data item that does
not have a name and whose value cannot change in a
program. There are six types of constants , but only 2
or 3 types are used.

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i) Decimal Fixed-point constants
ii) Decimal Floating-point constants( using E-
notation).
iii) Character string constants : up to 256 characters ,
must be enclosed by ‘ , if an apostrophe is a part of
data , then it should be preceded by another
apostrophe with no intervening blanks.The repetition
factors can be specified.
iv) Bit-string constants : It’s a series of binary digits
enclosed in single quotes and followed by the letter B.
Used as flag , setting 1 or 0 , repetition factor can be
used.
v) Binary Fixed-Point and Binary Floating-Point
constants .

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Data types :
FIXED DECIMAL Two digits/byte Comm. Appl
plus sign
FIXED BINARY Half word or Comm &
full word scientific appl
FLOAT DECIMAL Full word, Scientific appl
double word or Arithmetic
two double words
PICTURE One digit / byte
CHARACTER or One character/byte
PICTURE
BIT One byte Boolean oper
Purpose

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DECLARE statement :
The purposes :
i) For implicit declaration
ii) For data aggregation
iii) For input and output files
Base and Scale and precision attributes
DECLARE PRICE DECIMAL FIXED(5,2)
DECLARE PI FLOAT DECIMAL(6)
DECLARE COUNT FIXED BINARY(15)
DECLARE PI FLOAT BINARY(31)
DECLARE BETA FIXED BINARY(15,2)

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Storage classes :
Any data name occupies some space in the main
memory to hold the data , when this storage space will
be allocated to a data is decided depending on the
storage class of the data .
The types are :
1. Automatic ( Default )-- can be abbreviated as AUTO
2. Static
3. Based
4. Controlled --- can be abbreviated as CTL
Based : The address is delimited by a pointer variable.
E.g. DCL P POINTER;
DCL A(100) FIXED BASED(P);

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Address can be assigned in any of the following
ways:
1. By assigning the value returned by the ADDR
built-in function.
2. By assigning the value of another pointer.
3. With the SET option of a READ statement.
4. With the SET option of a LOCATE statement.
Controlled : Similar to based , in this programmer
has a greater degree of control in the allocation
of storage than he does for STATIC or
AUTOMATIC. DCL A(100) INIT( (100) 0)
CONTROLLED ;

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Partially declared identifiers :
1. The base : DCL A DECIMAL ; DCL B BINARY;
2. The scale : DCL C FIXED; DCL D FLOAT;
3. The base and precision : DCL AA
DECIMAL(16);
DCL BB BINARY(53);
4. The scale and precision : DCL CC FIXED(9,2) ;
DCL DD FLOAT(16);

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List-directed Input:
GET LIST (A,B,C,D);
GET LIST (A,B,C,D) COPY;
List-directed Output: The default line size for a
PUT LIST is 120 positions.
Different tab positions on the screen are :
column no 1,25,49,73,97,121( only be used to
print a record having length more than 120
characters). Different data items are printed
beginning at predetermined tab positions.

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PUT LIST (A,B,C,D);
PUT LIST (50,’abc’,123.445);
To print at a specified tab position ,i.e. without
preceding the previous position , specify a
character-string of a blank to the preceding tab
positions.
E.g. PUT LIST (50,’ ‘,’abc’,’ ‘,123.445);---
First value will be printed at col no 1, second
value at 49th col. , third value at 97th col , a
blank will be printed at both 25th and 73rd col
positions.

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Whenever PUT LIST statement is executed for the first
time , it automatically skips to a new page ,if you
want to print different values in different lines or
pages , SKIP and PAGE options can be used.
PAGE is used to advance to the top of a new page.
SKIP is used to advance by a number of lines
specified . If the no. of line is not specified , then
assumed as SKIP(1).
E.g. PUT PAGE LIST (‘ABC’);
PUT SKIP LIST (1212);
PUT SKIP(2) LIST(343);

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A skip(0) causes a suppression of the line feed.
E.g. PUT PAGE LIST (‘ SALES REPORT’);
PUT SKIP(0) LIST ((12)’_’) ;
To specify the line number :
e.g. PUT PAGE LINE(10) LIST(A,B,C);
-----------------------------------------------------------------
PUT PAGE;
PUT SKIP(2);
PUT LINE(10) ;

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The Assignment Statement :
e.g.TOTAL_COST = COST * QUANTITY;
A,B,C = 0;
The Arithmetic Operations :
There are five basic arithmetic operators :
Symbol Operations
1. ** Exponentiation
2. * Multiplication
3. / Division
4. + Addition
5. - Subtraction

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Concatenation :
The || symbol is used is to join string or Bit
data.
e.g. NAME1 = ‘IIS’;
NAME2 = ‘INFOTECH’
COMPANY_NAME = NAME1 || NAME2;
DATA1 = ‘1100’B;
DATA2 = ‘0011’B;
DATA3 = DATA1 || DATA2 ;
----This will store ‘11000011’B in DATA3.

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Built-in Functions :
The following are the classes of Built-in
functions :
1. Arithmetic function
2. Mathematical function
3. Array-handling function
4. String handling
5. Condition handling
6. Storage control
7. Miscellaneous

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Arithmetic function :
ABS(-44) --- 44
CEIL(3.333) --- 4
FLOOR(3.333) ---- 3
MIN(2,6,4) ---- 2
MAX(2,6,4) ---- 6
TRUNC(3.33) --- 3.00
SIGN(-4) --- -1
SIGN(0) ---- 0
SIGN(4) --- 1

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ROUND(123.456,1) --- 123.500
ROUND(123.456,2) --- 123.460
ROUND(123.456,0) ---- 123.000
ROUND(123.456,-1) ---- 120.000
ROUND(123.456,-2) ---- 100.000
ROUND(123.456,-3) ---- 0
MOD (25,6) --- 1
Mathematical function
SIN , COS , TAN , LOG , LOG10 , SQRT

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String handling
SUBSTR(‘IIS INFOTECH’,5,4) --- INFO
A CHAR(10) --- A = ‘ 10’
LENGTH(A) -- 3
REPEAT(‘A’,2) --- ‘AA’
TRANSLATE ( ‘CAT’,’C’,’B’) --- ‘BAT’
Miscellaneous
DATE returns date in the form of YYMMDD.
TIME returns current time in the form of
HHMMSSTTT.
When these functions are used they should be
explicitly declared as BUILTIN .

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UNSPEC ( identifier ) - Converts any identifier to
a BIT string.
DCL A CHAR(2) INIT(‘AB’);
PUT LIST (UNSPEC(A)); --- prints the binary
equivalent of ‘AB’
UNSPEC(A) = ‘0100000101000011’B; -- The
value ‘AC’ will be assigned to the variable A

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An example for Pseudo-variable:
BLANK : PROC OPTIONS(MAIN);
DCL NAME CHAR(15) INIT('NOW IS THE TIME');
DCL NAME1 CHAR(12) VARYING;
DCL I FIXED BINARY(15);
DCL J FIXED BIN(15) INIT(1);
DO I =1 TO LENGTH(NAME);
IF SUBSTR(NAME,I,1)=' '
THEN;
ELSE
DO;

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SUBSTR(NAME1,J,1)=SUBSTR(NAME,I,1);
J=J+1;
END;
END;
PUT LIST(NAME1);
END BLANK;

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Data Conversion: When mixed data types
appear in an arithmetic expression , data items
are converted to the data format of the other.
DECIMAL is converted to BINARY.
FIXED is converted to FLOAT.
BIT is converted to CHARACTER
A zero bit becomes a character 0.
Arithmetic to CHARACTER( length should be > 2 bytes)
CHARACTER to arithmetic
Arithmetic( without symbol) to BIT
BIT( always unsigned ) to arithmetic
CHARACTER to BIT

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Selection Construct (Logical testing) :
IF statement : The list of comparison operators ..
Symbols used are GE or >= , GT or > , NE , ~= ,LT or < ,
LE or <= , NL , NG .
The list of Logical operators ….
Symbols used are ~ or ^ , & , | .
IF condition1 THEN DO ………….;
………………;
………………;
END;
IF A=B THEN
IF A=C THEN X=1;
ELSE;
ELSE
X=3;

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The SELECT statement :
-----------------Format- 1-------------------------------------
SELECT ( identifier) ;
WHEN( value1) statement;
WHEN( value2) statement;
OTHERWISE statement ;
END;
-----------------Format - 2 ----------------------------------
SELECT ;
WHEN( cond1) statement;
WHEN( cond2) statement;
OTHERWISE statement ;
END;

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The Comparison and Logical operators in the
Assignment statement
e.g. A=B=C;
A=B>C;
A= B>C & D>E;
A=B>C | D>E;

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Conditions and On-units
During the execution of a PL/I program , a
number of conditions could arise causing a
program to interrupt.It may be the detection of
an unexpected error or of an occurrence that is
expected but at an unpredictable time.
Some conditions may be raised during file
handling :
! ENDFILE (filename) - ENDPAGE( filename)
! RECORD(filename) - TRANSMIT(filename)
They will be discussed during file handling only.

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Some conditions may be raised during arithmetic
operations :
! CONVERSION( default is enabled )
e.g. DCL X BIT(4);
X= ‘10A1’;
! SIZE (default is disabled)
e.g. DCL A FIXED DEC(4);
DCL B FIXED DEC(5) INIT(12345) ;
A=B;

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! FIXEDOVERFLOW( for fixed-point variables, default is
enabled)
e.g. DCL A FIXED DEC(5);
DCL B FIXED DEC(5);
DCL C FIXED DEC(5);
A=99999; B=88888;
C=A * B;
! OVERFLOW ( for floating-point variables, default is enabled)
e.g. A = 55E71; B = 23E11;
C=A*B;

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! UNDERFLOW ( for floating-point variables, default
is enabled)
e.g. A = 55E-71;
B = 23E-11;
C=A*B;
! ZERODIVIDE( default is enabled)
e.g. A=10;
B=0;
C=A/B;

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! CHECK (used for debugging, default is disabled)
(CHECK):
AVERAGE:PROC OPTIONS(MAIN);
:
GET LIST(A,B,C);
AVG=(A+B)/2;
PUT LIST(‘THE AVERAGE IS’, AVG);
END AVERAGE;
---- (CHECK(A,B)):
--- (CHECK):AVG=(A+B)/2;

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The status of Conditions :
Conditions are enabled or disabled through a
condition prefix , which is the name of one or
more conditions separated by commas,
enclosed in parentheses, and prefixed to a
statement by a colon. The word NO preceding
the condition name indicates that the condition
is to be disabled.
E.g. (NOFIXEDOVERFLOW):SUM=A+B+C;
(SIZE,NOFIXEDOVERFLOW):PROG1:PROC
OPTIONS(MAIN);
(NOSIZE):Y=A*B/C;

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/* An example of On - unit (SIZE) and pseudo-variable
(SIZE):
THIRD : PROCEDURE OPTIONS(MAIN);
DCL NAME CHAR(10) VARYING ,
I FIXED BIN(15),
A CHAR(1),
BITVAR BIT(8);
GET LIST(NAME);
DO I = 1 TO LENGTH(NAME);
A = SUBSTR(NAME,I,1);
UNSPEC(A) = UNSPEC(A) | '00100000'B;

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PUT SKIP LIST (UNSPEC(A));
SUBSTR(NAME,I,1) = A;
END ;
PUT LIST (NAME);
END THIRD;

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Changing the action taken :
ON statement is used to specify what action will
be taken if the condition arises.In the absence
of a program-supplied ON statement for an
enabled condition , standard system action will
be taken. If , after having supplied your own on-
unit for a condition , you wish to return to the
standard system action for that on-unit, simply
specify another ON statement with the keyword
SYSTEM.For multiple lines of actions enclose
the commands within BEGIN; …. END;

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ON ERROR BEGIN;
ON ERROR
SYSTEM;
:
:
SNAP ERROR
END;
Null action:
ON ENDPAGE ;
First time the error is encountered the
first ON ERROR will be executed
and after entering the BEGIN block
, if it encounters another error then
it will not execute the first one , but
the second one i.e. system will
handle the condition in the default
way.
SNAP ERROR is used to execute the
first ON ERROR even after the first
time execution instead of second
one.

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Simulating conditions :
Can simulate execution of any specified ON
condition statement by :
SIGNAL condition_name ;
If the specified condition is not enabled , then
it’ll be taken as null statement;
One of the uses of this statement is in program
checkout to test the action of an on-unit and
to determine that the correct program action
is associated with the condition.

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BUILT-IN FUNCTIONS FOR ON-UNITS
1. ONCODE : e.g. ON ERROR
PUT LIST(ONCODE);
2. ONLOC : e.g. MAIN: PROC OPTIONS(MAIN);
:
SUBRT:PROC;
:
:
END SUBRT;
END MAIN;
3. ONCHAR : e.g. CHAR=ONCHAR;
4. ONSOURCE : e.g. SOURCE=ONSOURCE;

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Iteration Constructs :
1. Label_name : DO WHILE( condition);
:
:
END label_name;
2. DO UNTIL(condition);
:
:
END;
3. DO I=n to m BY [+/-] x ;
4. DO M=1 TO 10,21 TO 30, 41 TO 50;

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5. DO K= 1 TO 5, 8 TO 18 BY 2 , 50 TO 55 BY 5, 40
TO 44;
6. DO J=3,12,6,5,45
7. DO I=n BY x;
:
:
END; /* some other condition must be mentioned to
come out of the loop , otherwise it’ll be an infinite
loop or FIXEDOVERFLOW will occur.*/
8. DO K=1 TO 10 WHILE ( A>10);

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9. DO K=1 TO 10,11 WHILE ( A>10);
10. DO K=1 TO 10,11 BY 0 WHILE ( A>10);
11. DO K=1 TO 10 UNTIL ( A>10);
12. DO NAME = ‘AAA’,’BBB’,’CCC’;
Nested DO-groups :
DO I=n TO M;
DO J= x TO y;
:
:
END;
END;

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Leaving a loop :
1. By assigning a greater value than the highest value
to the index variable
2. By GOTO statement which is not advised by
structured programming.
3. By LEAVE statement .
E.g. LEAVE block_name ; -- comes out from the
specified block
LEAVE ; -- comes out from the current block

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Array handling :
e.g. DCL DAY_NAMES(7) CHAR(10);
DCL LIST(-2:3) FIXED BIN(15,0)
INIT(10,20,15,25,30,40);
DCL TABLE(6,2) FIXED DEC (5);
DCL TABLE(-2:3,4:5) FIXED DEC(5) INIT (0);
-- only possible in Mainframe
DCL B(5,3) FIXED INIT ( (15)0);
DCL B(9,9) FIXED INIT ((81)-1);
DCL A(2,2) FIXED INIT(1,2,3,4);
DCL TABLE(10) CHAR(2) INIT((2)’A’);
-- only possible in Mainframe
DCL TABLE(10) CHAR(2) INIT((2) (2)’A’);

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DCL TABLE(10) CHAR(5) INIT((10) (1)’ABC’);
DCL A(3) INIT(10,*,30);
Array assignments:
Scalar to Array :
DCL MONTHS(12) FIXED(4,1);
MONTHS=0;
MONHS(5)=10.5;
Array to Array :
DCL A(5,5) ,B(5,5);
A=B;

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Array Expressions:
Prefix operators and Arrays:
1) A=-A;
Infix operators and Arrays:
1) B=A*5 ; --Every elements of A is multiplied
by 5 and stored in B.
2) A=A * A(1,2); -- Multiplies every elements by
the value of the element at (1,2) and stores the
data into A.
3) C=A +B;

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On conditions using String :
1. STRINGRANGE condition(default is
disabled)
2. STRINGSIZE condition (default is enabled)
On conditions using Array :
1.SUBSCRIPTRANGE condition(default is
disabled)

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Array cross-sections:
B(*,3) ; B(5,*); B(*,*) i.e. B ;
e.g. S=SUM(B(*,3))
An example on Matrix multiplication :
C=0;
DO I=1 TO L;
DO J=1 TO N;
DO K=1 TO M;
C(I,J)= A(I,K) * B(K,J) +C(I,J);
END;
END;
END;

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An example on Matrix multiplication using
cross sections :
C=0;
DO I=1 TO L;
DO J=1 TO N;
C(I,J)= SUM(A(I,*) * B(*,J));
END;
END;

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/* An example using array */
REVERS:PROC OPTIONS(MAIN);
DCL STR1(10) FIXED (10)
INIT(1,2,3,4,5,6,7,8,9,10);
DCL STR2(10) FIXED (10) ;
DCL I FIXED (15);
DCL J FIXED (15) INIT(1);
DO I =10 TO 1 BY -1 ;
STR2(J)=STR1(I);
J=J+1;
END;
PUT LIST(STR2);
END REVERS;

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/* An example to sort data stored in an array */
SORT1 : PROC OPTIONS (MAIN);
DCL ARRAY1(10) FIXED (10);
DCL I FIXED(2), J FIXED(2), TEMP FIXED(2);
PUT LIST ('ENTER 10 NUMBERS');
DO I = 1 TO 10;
PUT SKIP LIST ( 'ENTER NO. ',I);
GET (ARRAY1(I));
END;
DO I = 1 TO 9;
DO J = I+1 TO 10;

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IF (ARRAY1(I) > ARRAY1(J) THEN
DO;
TEMP = ARRAY1(I);
ARRAY1(I) = ARRAY1(J);
ARRAY1(J) = TEMP;
END;
END;
END;
DO I = 1 TO 10;
PUT (ARRAY1(I));
END;
END SORT1;

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/* An example to handle two arrays */
STARR:PROC OPTIONS(MAIN);
DCL 1 HISTORY (2),
2 NAME CHAR(20) ,
2 GRADE FIXED(4,1);
DCL 1 HONOR_STUDENT(2),
2 NAME CHAR(20) ,
2 GRADE FIXED(4,1);
DCL I FIXED DEC(1) INIT(1);
PUT LIST('ENTER DATA OF STUDENTS:');

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DO I=1 TO 2;
PUT SKIP LIST('ENTER NAME');
GET LIST(HISTORY(I).NAME);
PUT SKIP LIST('ENTER GRADE');
GET LIST(HISTORY(I).GRADE);
END;
DO I=1 TO 2;
IF HISTORY(I).GRADE>=92.5 THEN
DO;
HONOR_STUDENT(I).NAME
=HISTORY(I).NAME;
HONOR_STUDENT(I).GRADE =
HISTORY(I).GRADE;

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END;
END;
DO I=1 TO 2;
PUT SKIP LIST('NAME IS');
PUT LIST(HONOR_STUDENT(I).NAME);
PUT SKIP LIST('GRADE IS');
PUT LIST(HONOR_STUDENT(I).GRADE);
END;
END STARR;

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Controlled storage with array bounds
determined dynamically :
CONTR : PROC OPTIONS(MAIN);
DCL ( A(*,*),B(*,*),C(*,*)) CONTROLLED;
GET LIST(I,J); ALLOCATE A(I,J),B(I,J);
GET LIST(A,B); CALL ADDAR(A,B,C);
PUT LIST(C);
ADDAR : PROC(R,S,T);
DCL (R(*,*),S(*,*) ,T(*)) CONTROLLED;
ALLOCATE T(LBOUND(R,1) :
HBOUND(R,1));
L1: DO K=LBOUND(R,1) TO HBOUND(R,1);
T(K)=0;

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L2 : DO I=LBOUND(R,2) TO HBOUND(R,2);
T(K)=R(K,J) + S(K,J) + T(K);
END L2;
END L1;
FREE R,S;
END ADDAR;
END CONTR;
/* Note : C can be passed as an argument although it
has not yet been allocated. */

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Array manipulation and built-in functions :
The DIM built-in
The LBOUND built-in
The HBOUND built-in
The SUM built-in
The PROD built-in

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I/O operations and Arrays :
e.g. DCL AMOUNT(5) FIXED DEC(3);
GET LIST(AMOUNT);
e.g. DCL TABLE(6,2) FIXED DEC(3);
GET LIST (TABLE);
The Repetitive specification of a data item :
e.g.DCL DAY_NAMES(7) CHAR(10);
GET LIST( (DAY_NAMES(I) DO I=1 TO 7) );
e.g.DCL TABLE(6,2) FIXED DEC (5);
GET LIST ((( TABLE(I,J) DO I=1 TO 6) DO J=1 TO 2));
e.g. GET LIST((A(I) DO I=1TO 5),(B(J),C(J) DO J=1 TO
3));

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Structures :
DCL 1 EMP_DET,
2 EMP_NO FIXED DEC(5) ,
2 EMP_NAME CHAR(20),
2 EMP_SALARY,
3 BASIC FIXED (9,2),
3 INDIA_ALLOW FIXED(9,2),
3 MEDICAL(12),
4 MED_MONTH FIXED(9,2);
The statement could be written in a continuous
string also.

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Array of Structures :
DCL 1 EMP_DET(100),
2 EMP_NO FIXED DEC(5) ,
2 EMP_NAME CHAR(20),
2 EMP_SALARY,
3 BASIC FIXED (9,2),
3 INDIA_ALLOW FIXED(9,2),
3 MEDICAL(12),
4 MED_MONTH FIXED(9,2);
If attribute are to be explicitly declared in a
structure, they may only be specified for
elementary items.

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e.g. DCL EMP_DET1 CHAR(100);
EMP_DET1=EMP_DET; ---- ERROR
e.g. DCL EMP_DET1 LIKE EMP_DET;
--it’ll copy the structure of EMP_DET to
EMP_DET1.
e.g. EMP_DET1=EMP_DET , BY NAME ;
-- it’ll only copy the elements having the same
names.
e.g. EMP_DET1=‘ ‘;
-- it’ll assign the same space to all character
elements.
Overlay defining:
e.g. DCL EMP_DET2(100) DEFINED EMP_DET;

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Built-in Functions for structures :
STRING function : It concatenates all the
elements in an array or a structure into a single
character or bit-string element .Thus, if it is
desired to concatenate a number of elementary
items found in a structure or array , it would be
easier to code the STRING function than to
code the concatenation operation a number of
times. STRING may also be used as a pseudo-
variable.

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E.g.
DCL 1 EMP_DET,
2 EMP_NO CHAR(2) INIT(‘11’),
2 EMP_NAME CHAR(20) INIT(‘ JOAN K.
HUGHES’),
2 EMP_ADD CHAR(30) INIT(‘JOHN WILEY
& SONS ,ENGLAND’);
DCL ITEM CHAR(45);
ITEM=EMP_DET; --illegal
ITEM=STRING(EMP_DET);
EMP_DET=ITEM;
STRING(EMP_DET)=ITEM;

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Pictures :
The pictures are used for the following purposes :
1.To treat character-strings as arithmetic quantities.
2. To treat arithmetic quantities as character-strings.
3. To edit data
4. To validate data
The general form of pictures for editing and validating is
: PICTURE ‘picture specification characters’
There are two types of pictures :
1. Decimal pictures
2. Characters-string pictures

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Decimal pictures : The base and scale are
implicitly DECIMAL and FIXED respectively.
e.g DCL A PICTURE ‘9999V99’;
DCL B PICTURE ‘(4)9V9(2);
DCL C PICTURE ‘S9999V99;
DCL D PIC ‘999S’;
Editing data for printed output :
Using Z , . , B, /, $, S, +, -, *,CR, DR AND , .
E.g. DCL A PIC’****$S9,999V.99CR’;
A=1234.54;
PUT LIST(A); ------ The output is : *1234.54

70
Character-string pictures :
The symbols used are : A, X, 9 .
E.g. DCL NAME PIC ’(20)A’;
DCL ADDRESS PIC ‘(20)X;
DCL PINCODE PIC ‘999999’;
Pictures in Stream I/O :
Some editing of data in stream I/O is
automatic.In list-directed and data-directed
output of arithmetic coded data , leading zeros
will be suppressed and minus sign and decimal
point inserted if necessary.

71
Full editing capability may be achieved in list-
directed output by simply assigning data items
to identifiers that have the PICTURE attribute
and then issuing a PUT LIST on those
identifiers.In edit-directed I/O, full editing of data
may be implemented by using a format item
called P-format , containing any
character allowed in PICTURE and used to
describe the characteristics of external data.
E.g. DCL VALUE FIXED DEC(8,2);
DCL EDIT_DATA PIC’$$$$.$$$V.99CR’;
VALUE=A*B;

72
P’picture specification’ :
e.g. GET FILE(SYSIN) EDIT(A,B,C,D) (COL(1) ,
P’ZZZ9’, P’99V99’,P’AA999’,P’(5)9);
e.g. DCL ASSETS FIXED DEC(11,2);
ASSETS = 45326985.76;
PUT EDIT (ASSETS) (P’$$$$,$$$,$$$V.99’);
The output is : b$45,326,985.76

73
e.g. ASSETS=2500.00;
PUT EDIT(ASSETS) (P’$ZZ,ZZZ,ZZZV.99’);
The output is : $bbbbb2,500.00
e.g. DCL TODAY CHAR(6);
TODAY=‘080880’;
PUT EDIT(TODAY)(P’99/99/99’);
The output is 08/08/80

74
Procedures:
Sub-routine procedures :
1. Invoked by CALL statement
2. Separately compiled ,from the invoking
procedures, called as external procedures .
3. The length of these procedures’ names is
limited to 7 or 8 characters.
4. A STOP or EXIT statement in both separately
compiled procedure and nested sub-routine
procedure , abnormally terminates execution
of that sub-routine and of the entire program
associated with the procedure that invoked it.

75
5. Ideally an external sub-routine should not terminate
the entire program , should return an error indicator
to the calling program indicating whether or not an
error has been detected during the execution of the
sub-routine. It’s the function of MAIN program to
decide what action is taken.
6. Arguments passed to a called procedure must be
accepted by parameters of the calling procedure.
7. A built-in functions may be specified as arguments to
other subprogram , that function is

76
may be executed before the subroutine is called and
the value is being passed when there is no argument
of that built-in or the name of the built-in is enclosed
by parentheses or the built-in is passed to another
built-in as an argument. Otherwise the name is passed
to the sub-routine.
8. If arguments and parameters are of same type, then
the parameters share the same memory area of that
of parameters , called as call by reference.
9. If arguments and parameters are of different types or
constants , then the different memory area is allocated
to the parameters , called as call by value.

77
Dummy arguments :There are created in the
following cases:
1) If an argument is a constant
2) If an argument is an expression involving
operators.
3) If an argument is an expression in
parentheses.
4) If an argument is a variable whose attributes
are different from the attributes declared for the
parameter in an entry name attribute
specification appearing in the invoking block.
5) If an argument is itself a function reference
containing arguments.

78
The ENTRY attribute :It directs the compiler( in
Mainframe only) to generate the coding to convert one
or more arguments to conform to the attribute of the
corresponding parameters .Declare the sub-routine
within the main procedure as:
DCL SUBRT ENTRY(types of parameters);
After conversion , the values are stored in dummy
arguments in different locations and names are
automatically assigned by compiler, which can not be
accessed by programmers.Any manipulation done by
the called procedure only effects those dummy
arguments and hence original arguments remain
unchanged.

79
/* An example of Sub-routine using ENTRY( CALL BY
VALUE)*/
SUBPR : PROC OPTIONS(MAIN);
DCL A FIXED BINARY(15) INIT(10),
B FIXED BINARY (15) INIT(15),
C FIXED BINARY(15);
DCL ADDP ENTRY ( FIXED DEC(15), FIXED DEC(15), );
CALL ADDP(A,B,C);
PUT LIST(C);
ADDP : PROC(A,B,C);
DCL A FIXED DEC(15),
B FIXED DEC(15),
C FIXED BIN(15);
C=A+B;
END ADDP;
END SUBPR;

80
The External attribute:
Specifies a name to be known to other
procedures containing an EXTERNAL
declaration of the same name( must be
limited to 6 characters).
PROG: PROC OPTIONS(MAIN);
DCL ARRAY(200) FIXED EXTERNAL;
DCL SUM FIXED(7) EXTERNAL;
GET LIST(ARRAY);
CALL ADDSUM;
PUT LIST(‘RESULT IS’,SUM);

81
ADDSUM : PROC;
DCL ARRAY(200) FIXED EXTERNAL;
DCL SUM FIXED(7) EXTERNAL;
SUM=0;
DO K=1 TO 200
SUM=SUM+ARRAY(K);
END;
END ADDSUM;
END PROG;

82
/* An example of Sub-routine using builtin */
TIMED: PROC OPTIONS(MAIN);
DCL TIME BUILTIN;
DCL TSTR CHAR(8) ;
CALL CTIME ((TIME),TSTR);
PUT LIST (TSTR);
CTIME:PROC(T,X) ;
DCL T CHAR(9);
DCL X CHAR(8);
DCL A CHAR(2);

83
DCL B CHAR(2);
DCL C CHAR(2);
A=SUBSTR(T,1,2);
B=SUBSTR(T,3,2);
C=SUBSTR(T,5,2);
X=A || ':’ || B || ':’ ||C;
END CTIME;
END TIMED;

84
Function Procedures:
1. A function is a procedure that returns a single value
to the invoking procedure.
2. Invoked in the same manner as PL/I built-in
functions are referenced.
3. Should not be invoked by CALL statement.
4. The RETURN statement is used to terminate a
function and a single value to the point of
invocation.
CALC:PROCEDURE(A,B,C);
RETURN(A+B+C);
END CALC;

85
5. By default , if the function name begins with
the letters A to H or O to Z , then the result
will be DECIMAL FLOAT(6).
Names starting with I to N return a result with
the attributes FIXED BINARY (15).
D=CALC(A,B,C);
To return data of some other type , use
RETURNS keyword , in both invoking and
invoked procedures.

86
CALC:PROCEDURE(A,B,C) RETURNS(FIXED
DECIMAL(7));
RETURN(A+B+C);
END CALC;
6. The RETURNS keyword , when specified in a
PROCEDURE or ENTRY statement , is
referred to as the RETURNS option.In the
previous example , the invoking procedure
must also specify that CALC is returning a
FIXED DECIMAL value of the same precision
because these attributes differ from the
default.

87
The RETURNS attribute , specified in a DECLARE
statement for an entry name , indicates the
attributes of the value returned by that function.
MAIN: PROCEDURE OPTION(MAIN);
DCL CALC ENTRY RETURNS (FIXED DEC(7));
DCL SUM FIXED DEC(7);
GET LIST (A,B,C);
SUM=CALC(A,B,C);
:
:
END MAIN;

88
/* An example of Function */
SUBPR : PROC OPTIONS(MAIN);
DCL A FIXED BINARY(15) INIT(10),
B FIXED BINARY (15) INIT(15),
C FIXED BINARY(15);
C= ADDP(A,B);
PUT LIST(C);
ADDP : PROC(A,B) RETURNS(FIXED BIN(15));
C=A+B;
RETURN (C);
END ADDP;
END SUBPR;

89
/* An example of function using builtin */
TIMED: PROC OPTIONS(MAIN);
DCL TIME BUILTIN;
DCL TRES CHAR(8) ;
TRES= CTIME (TIME);
PUT LIST (TRES);
CTIME:PROC(T,X) RETURNS(CHAR(8));
DCL T CHAR(9);
DCL X CHAR(8);
DCL A CHAR(2);
DCL B CHAR(2);

90
DCL C CHAR(2);
A=SUBSTR(T,1,2);
B=SUBSTR(T,3,2);
C=SUBSTR(T,5,2);
X=A || ':’ || B || ':’ ||C;
RETURN(X);
END CTIME;
END TIMED;

91
Recursive procedures :
When a procedure invokes itself , its said to be
recursive.
e.g. the computation of factorial where
n! = 1*2*3…….*n
----code in the calling procedure--------
N=4;
RESULT=CALC_FACT(N);
-----code in the called procedure ---------
CALC_FACT:PROCEDURE(M);
K=1;

92
DO I=1 TO M;
K=K*I;
END;
RETURN(K);
END CALC_FACT;
-----code using RECURSIVE option-----------
CALC_FACT:PROCEDURE(M) RECURSIVE;
K=M - 1;
IF K=1 THEN
I=M;
ELSE
I=M * CALC_FACT(K);
RETURN(I);
END CALC_FACT;

93
File declarations :
1. Define the file via a DECLARE statement.
-- DECLARE EMPLOYEE FILE(other attributes);
Attributes associated with a file include the type
of transmission ( STREAM or RECORD) , the
direction of transmission (INPUT ,OUTPUT ,
UPDATE in the case of disk files ) and the
physical environment of the file e.g. ENV /
ENVIRONMENT to specify BLKSIZE or
RECSIZE or record type( F,V,VB,FB) or device
type.

94
---- DECLARE EMPLOYEE FILE INPUT STREAM
ENV (options);
2. File must be opened before communicating via
OPEN statement and can also provide additional file
attributes at open time.
File attributes :
1. FILE attribute
2. INPUT/OUTPUT attribute
3. STREAM attribute
4. ENVIRONMENT attribute
5. PRINT attribute

95
The OPEN statement :
Files are opened automatically , hence not
required to give the command explicitly . But
still used to specify the additional file attributes
and/or options may be specified at open times.
OPEN FILE(FILE1), FILE(FILE2);
OPEN FILE(FILE1) PAGESIZE(50);
OPEN FILE(FILE1) LINESIZE(121);

96
3. Process information in the file via READ or
WRITE or REWRITE or GET or PUT
statements.
Default of pre-defined files :
When not mentioned in GET or PUT statement
, SYSIN is for the standard input or SYSPRINT
for the output file.
E.g. GET LIST (A,B,C); --- is equivalent to
GET FILE(SYSIN) LIST (A,B,C):
4. Close the file via CLOSE statement.
CLOSE FILE (EMPLOYEE);

97
In the initial design of PL/I , stream I/O was
intended for scientific applications. Now-a-
days stream I/O is used in both scientific and
commercial programming applications ,
although the majority of commercial
applications use record I/O . Stream I/O is
most often used for a terminal or printer files ,
although it could also be used for tape or disk
unblocked records in consecutive files.

98
Stream I/O :
All input and output data items are in the form of
stream of characters. In input stream , characters are
converted to the internal attributes of the identifiers
specified in the GET statement. On output , coded
arithmetic data items are automatically converted back
to character form before the output takes place.
There are three types :
1. List-directed I/O
2. Edit-directed I/O
3. Data-directed I/O

99
Edit-directed I/O:
1. The format of the data items must be
mentioned.
2. General format :
GET EDIT (data list)(format list);
PUT EDIT (data list)(format list);
e.g. GET EDIT (EMP_NO , EMP_NAME,
BASIC, INDIA_ALLOW, MED_MONTH )
(COLUMN(1), F(5) , A(20),F (9,2), F(9,2),
F(9,2));
e.g. GET EDIT (EMP_NO , EMP_NAME,
BASIC, INDIA_ALLOW, MED_MONTH )
(R(RFMT));

100
:
RFMT: FORMAT(COLUMN(1), F(5) , A(20),F (9,2),
F(9,2), F(9,2));
Rules :
a) All data list items have corresponding format
items
b) If there are more format than data items , there
is a return to the beginning of the format list.
E.g. GET EDIT(A,B,C) (F(4),F(5));
c) The data list item need not have the same width
specification as the corresponding format items.

101
E.g. DCL NAME CHAR(15);
GET EDIT (NAME) (A(20));
d) I/O continues until the data list is
exhausted.
e) Input data items may be pseudo-variables
e.g. DCL NAME CHAR(20);
GET EDIT (SUBSTR(NAME,5,10)) (A(20));
f) Data list items may be names of data
aggregates.
E.g. DCL TABLE(10) FLOAT DEC(6);
GET EDIT(TABLE)
(COLUMN(1),F(6,2));

102
Equivalent to :
E.g. GET EDIT ((TABLE (I) DO I=1 TO 10))
(COLUMN(1),F(6,2));
E.g.DCL TABLE(2,5) FLOAT DEC(6);
PUT EDIT (TABLE) (F(10));
Equivalent to:
e.g. GET EDIT ( ( (TABLE(I,J) DO J=1 TO 5)
DO I=1 TO 2) ) (F10));

103
Equivalent to :
DO I=1 TO 2;
DO J=1 TO 5;
GET EDIT (TABLE(I,J)) (F10));
END;
END;
g) Output data items may be built-in functions
h) Output data items may be PL/I constant
i) Data items may consists of Element Expression
j) More than one data list and corresponding format list
may be specified

104
e.g. GET EDIT (data list1) (format list1) (data list2)
(format list2) …;
3. A file name could also be specified :
GET FILE(filename) EDIT (data list)(format
list);
PUT FILE(filename) EDIT (data list)(format
list);

105
Data-directed I/O:
Data-directed Input:
Each item in the input is in the form of an
assignment that specifies both the value and
the variable to which it is to be assigned.
E.g. GET DATA (list of items); -- its optional and
maxm 320 items can be mentioned.
A=12.3, B=23, C=‘ABCDEF’,D=‘10101’B;
GET DATA (C,B,A,D);
GET DATA (A,B,C,D,E); --- E is not altered by the
input operation.

106
GET DATA (A,B); --- error as C,D are in the input
stream but not in the data list. And raises the NAME
condition.
ON NAME (SYSIN)
BEGIN;
:
:
END;
GET DATA; --the names in the stream may be any
names known at the pint of the GET statement. A data
list in the GET statement is optional ,because the
semi-colon determines the number if items to be
obtained from the stream.

107
If the data includes the name of an array , subscripted
references to the array may appear in the stream,
although subscripted names cannot appear in the data
list. The entire array need not appear in the stream ,
only those elements that actually appear in the stream
will be assigned .
E.g. DCL TABLE(10) FIXED (5,2);
GET DATA (TABLE);
the input stream consists of the following assignment
statements:
TABLE(3)=34.34; TABLE(10)=12.12;

108
Data-directed output :
Each data item is placed in the stream in the form of
assignment statements separated by blanks. The last
item output by each PUT statement followed by a
semicolon.Fixed point binary and floating point binary
data appear in fixed-point decimal format.
DCL A FIXED DEC(5) INIT(0);
DCL B FIXED DEC(5) INIT(0);
DCL C FIXED BIN(5) INIT(170);
PUT DATA(A,B,C); PUT PAGE DATA(A,B,C);
PUT SKIP(3) DATA(A,B,C); PUT LINE(5)
DATA (A,B,C);

109
The output to the default file SYSPRINT in the
format :
A=0 B=0 C=170;
If the output is to other than a printer , one
blank is placed between each assignment
statement.
The data list may be an element , array , a
subscripted name, structure or a repetitive
specification involving any of these elements or
further repetitive specification.
PUT DATA;
PUT PAGE DATA (‘SALES REPORT’); --error

110
GET FILE (filename) DATA(A,B,C);
Data to be entered as:
: A=……, B=…… , C=…….
PUT FILE(filename ) DATA(A,B,C);
The COUNT Built-in function:
DCL INFILE FILE INPUT STREAM;
GET FILE (INFILE) DATA;
I=COUNT(INFILE); /* no of elements is stored */
Output data item may be Built-in function:
PUT EDIT (DATE)(P’99/99/99’);

111
Example:
ON ENDFILE (DATA)
MORE_RECORDS=NO;
MORE_RECORDS=YES;
READ FILE(DATA) INTO(DATA_AREA);
DO WHILE (MORE_RECORDS);
WRITE FILE(PRINT_FILE) FROM (DATA_AREA);
READ FILE(DATA) INTO(DATA_AREA);
END;

112
Conditions and On-Units :
The ERROR condition is raised as a result of the
standard system action and terminate the program
and return control to the O.S.
The ON statements are used to specify action to be
taken when a specified condition causes a program to
interrupt.
E.g. ON condition on-unit;
In absence of any of these On-Units specified in the
program, system will raise ERROR condition.The
following conditions are by default enabled , can not
be disabled.

113
1.ENDFILE(filename) 2. ENDPAGE(filename)
3. RECORD(filename) 4.TRANSMIT(filename)
5. CONVERSION 6. SIZE
ON ENDFILE : This condition is raised during a
GET or READ operation.
ON ENDPAGE :This condition is raised when a
PUT statement results in an attempt to start a
new line beyond the limit specified for
PAGESIZE( specified in OPEN statement).

114
ON KEY condition : Raised during operations on
keyed records in any of the following cases:
1. The keyed record can not be found for a READ or
REWRITE statement.
2. An attempt is made to add a duplicate key by a
WRITE statement.
3. The key has not been correctly specified.
4. No space is available to add the keyed record.
E.g. ON KEY(FILE1)
BEGIN;
FLAG=YES;

115
CODE=ONCODE;
PUT SKIP EDIT(‘KEY ERROR FOR
FILE1 , ONCODE IS’,CODE) (A);
END;
:
:
READ FILE(FILE1) INTO(DATA_AREA)
KEY(PARTNO);
IF FLAG THEN
CALL ERR-ROUTINE;
ELSE
CALL UPDATE_ROUTINE;

116
ON UNDEFINEDFILE condition : Raised whenever an
attempt to open a file is unsuccessful.
1. A conflict in attributes exists.
2. Attributes are incomplete.
ON RECORD condition : Raised during a
READ,WRITE , REWRITE operation. The input
operations it is raised by either of the following :
1. The size of the record on the data set is greater
than the size of the variable into which the record is to
be read ( for F,V,U format).

117
2. The size of the record is less than the size of
the variable ( for F format).
For a WRITE or REWRITE operations:
1. When the size of the variable from which the
record is to be written is greater than the
maximum size specified for the record (F,V,U
formats).
2. When the size of the variable is less than the
size specified for the record ( F format).
ON TRANSMIT condition :This condition is
raised due to any hardware malfunction . It
indicates that the data transmitted is incorrect.

118
Built-In Functions :
ONKEY : It extracts the value of the key for the
record that caused an I/O condition to be
raised.
E.g. DCL KEY_ERRCHAR(9) VARYING;
DCL ONKEY BUILTIN;
ON KEY(FILE1)
BEGIN;
KEY_ERR=ONKEY;
:
:
END;

119
ONFILE : It determines the name of the file for which an
I/O or CONVERSION condition was raised and
returns that name to point of invocation.
E.g. DCL NAM CHAR(3) VARYING;
DCL ONFILEBUILTIN;
ON KEY(FILE2)
BEGIN;
NAME=ONFILE;
:
:
END;

120
Record I/O :
1. Declare the file by DECLARE statement :
e.g. DCL DATA FILE INPUT RECORD ENV
(F RECSIZE (80) );
DCL PRINT_FILE OUTPUT RECORD ENV
( F RECSIZE (80) );
DCL DATA_AREA CHAR(80);
2. The keyword RECORD specifies the type of
I/O .
3. The record I/O statements that are used to
communicate with files include READ, WRITE,
REWRITE and DELETE.

121
Carriage control in Record I/O :
1. The program counter is automatically incremented as
and when a WRITE command is used.
2. When program counter reaches the maximum line per
page , the program gives the command to skip the
page to the printer.
3. To accomplish the carriage control for record output ,
append an extra character to the beginning of each
record.
4. A keyword must be added to the ENVIRONMET
section of the file declaration to notify PL/I that

122
these carriage control characters are being
used in the program and that the I/O routines
are to interpret the first character of each record
accordingly.
5. Two different sets are CTLASA or CTL360 .
6. If CTLASA is used , the carriage control
operation is performed before the printing , in
case of CTL360 , after printing.
7. Generally CTL360 characters are faster than
CTLASA.

123
Example :
LINECNT: PROC OPTIONS(MAIN);
DCL DATAIN FILE INPUT RECORD ENV(F
RECSIZE(80));
DCL FILE INPUT RECORD ENV
(F RECSIZE(80));
DCL PRINT_FILE FILE OUTPUT RECORD ENV
(F RECSIZE(81) CTLASA );
DCL DATA_AREA CHAR(80);
DCL LCTR FIXED(3);
DCL MORE_RECORDS BIT(1);

124
DCL NO BIT(1);
DCL PRINT_AREA CHAR(81);
ON ENDFILE(DATAIN)
MORE_RECORDS=NO;
OPEN FILE(DATAIN), FILE(PRINT_FILE);
LCTR=55;
READ FILE(DATAIN) INTO(DATA_AREA);
DO WHILE (MORE_RECORDS);
LCTR=LCTR+1;
IF LCTR>55 THEN
DO;

125
PRINT_AREA=‘1’ || DATA_AREA;
LCTR=0;
END;
ELSE
PRINT_AREA=‘ ‘ ||DATA_ARE;
WRITE FILE(PRINT_FILE) FROM
(PRINT_AREA);
READ FILE(DATAIN) INTO(DATA_AREA);
END;

126
File Organization :
1. Types of file access are ,SEQUENTIAL and
DIRECT.
2. Types of file organization are ,
CONSECUTIVE (sequential) , INDEXED(
indexed sequential) , REGIONAL(direct or
random) , VSAM( ESDS, KSDS, RRDS).
3.Different file attributes :
a) FILE b) EXTERNAL/INTERNAL
c) STREAM/RECORD
d) INPUT/ OUTPUT/ UPDATE

127
/*AN EXAMPLE TO CREATE AN INDEXED FILE FOR
STUDENT DATA */
WRprogram : PROC OPTIONS(MAIN);
DCL STUD FILE OUTPUT INDEXED RECORD;
DCL 1 STUD_DATA,
2 STUD_ROLL FIXED BINARY(15),
2 STUD_NAME CHAR(20),
2 STUD_MARKS FIXED BIN(15);
DCL CONT CHAR(1) INIT('Y');

128
DO WHILE (CONT='Y');
PUT SKIP LIST ('ENTER DATA FOR STUDENT');
PUT SKIP LIST ('ENTER ROLL FOR STUDENT');
GET LIST (STUD_ROLL);
PUT SKIP LIST ('ENTER NAME FOR STUDENT');
GET LIST(STUD_NAME);
PUT SKIP LIST ('ENTER MARKS FOR STUDENT');
GET LIST (STUD_MARKS);
WRITE FILE(STUD) FROM (STUD_DATA)
KEYFROM(STUD_ROLL) ;

129
PUT SKIP LIST ('WANT TO CONT(Y/N)?');
GET SKIP LIST (CONT);
END;
CLOSE FILE(STUD);
END WRprogram;

130
/* MENU PROGRAM TO CALL DIFF. PROGRAMS */
MENUprogram: PROC OPTIONS(MAIN);
DCL RDprogram EXT ENTRY;
DCL WRprogram EXT ENTRY;
DCL MODprogram EXT ENTRY;
DCL CH CHAR(1);
PUT SKIP LIST (' MENU ');
PUT SKIP LIST (' 1. TO ADD A RECORD');
PUT SKIP LIST (' 2. TO READ A RECORD');
PUT SKIP LIST (' 3. TO MODIFY A RECORD');
PUT SKIP LIST (' 4. EXIT ');

131
PUT SKIP(2) LIST ('ENTER YOUR CHOICE(1-4):');
GET LIST(CH);
IF CH='1’ THEN
CALL WRprogram;
ELSE
IF CH='2' THEN
CALL RDprogram;
ELSE
IF CH='3' THEN
CALL MODprogram;

132
ELSE
IF CH='4' THEN
RETURN;
ELSE
PUT LIST ('WRONG CHOICE');
END MENUprogram;

133
/* TO CREATE A FILE FOR STUDENT DATA */
WRprogram : PROC ;
DCL STUD FILE OUTPUT RECORD;
DCL 1 STUD_DATA,
/*OPEN FILE STUD OUTPUT;*/
PUT SKIP LIST ('ENTER DATA FOR STUDENT');
PUT SKIP LIST ('ENTER ROLL FOR STUDENT');

134
PUT SKIP LIST ('ENTER NAME FOR STUDENT');
PUT SKIP LIST ('ENTER MARKS FOR STUDENT');
WRITE FILE(STUD) FROM (STUD_DATA) ;
PUT SKIP LIST ('WANT TO CONT(Y/N)?');
GET SKIP LIST (CONT);
END;
CLOSE FILE(STUD);
END WRprogram;

135
/* TO MODIFY FILE FOR STUDENT DATA */
MODprogram : PROC ;
DCL STUD FILE UPDATE RECORD;
DCL 1 STUD_DATA,
/*OPEN FILE STUD INPUT;*/
DCL RNO FIXED BINARY(15);

136
ON ENDFILE(STUD)
BEGIN;
PUT SKIP LIST('RECORD NOT FOUND');
GO TO OUT;
END;
PUT SKIP LIST('ENTER ROLL NO TO BE
MODIFIED');
GET LIST(RNO);
READ FILE(STUD) INTO (STUD_DATA) ;
SEARCH : IF STUD_ROLL=RNO THEN
BEGIN;

137
PUT LIST ('ENTER NEW DATA');
PUT SKIP LIST ('ENTER NEW ROLL FOR
STUDENT');
PUT SKIP LIST ('ENTER NEW NAME FOR
STUDENT');
PUT SKIP LIST ('ENTER NEW MARKS FOR
STUDENT');
REWRITE FILE(STUD) FROM (STUD_DATA) ;
GO TO OUT;

138
END;
ELSE
BEGIN;
GOTO SEARCH;
END;
OUT: PUT SKIP LIST('WANT TO CONT(Y/N):');
GET LIST(CONT);
END;
CLOSE FILE(STUD);
END MODprogram;

139
/* TO READ FILE FOR STUDENT DATA */
RDprogram : PROC ;
DCL STUD FILE INPUT RECORD;
DCL 1 STUD_DATA,
/*OPEN FILE STUD INPUT;*/
DCL FLAG CHAR(1) INIT('Y');
ON ENDFILE(STUD)
FLAG='N';
PUT SKIP LIST('END OF FILE');

140
DO WHILE (FLAG='Y');
PUT SKIP LIST(STUD_ROLL);
PUT SKIP LIST(STUD_NAME);
PUT SKIP LIST(STUD_MARKS);
READ FILE(STDATA) INTO (STUD_DATA) ;
END;
CLOSE FILE(STUD);
END RDprogram;

Introduction to IBM PL/1 Programming Language

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