C programming session 05

of 31Ver. 1.0
Programming in C
In this session, you will learn to:
Work with arrays
Appreciate preprocessor directives
Objectives

of 31Ver. 1.0
Programming in C
Working with Arrays
Arrays:
Are a group of similar objects.
Can be defined as a contiguous area in memory.
Can be referred to by a common name.
Has a unique identifier for each element, called as a subscript
or an index.
Can be categorized as:
One-dimensional/Single-dimensional arrays
Multidimensional arrays

of 31Ver. 1.0
Programming in C
One-Dimensional Arrays
The syntax for declaring a one-dimensional array is:
type arrayname[n];
For Example:
char string [11];
Defines a character array named string to store 10
characters.
string[0] to string[9] are for valid characters.
string[10] for the string-terminator character, 0 (NULL).
Similarly:
int numbers [11];
Defines an integer type array called numbers to store 11
integers.
Integers are stored in numbers[0] to numbers[10].

of 31Ver. 1.0
Programming in C
Practice: 3.1
1. Write the array definition statements for storing the following
data:
a. Ten amounts with paisa.
b. Five ages to be stored in years and six non-fractional
quantities.
c. A thirty character long name.

of 31Ver. 1.0
Programming in C
Practice: 3.1 (Contd.)
Solution:
a. float fnum[10];
b. int age[5], qty[6];
c. char name[31];

of 31Ver. 1.0
Programming in C
Initializing Arrays:
An array can be initialized, when declared.
Initialization at the time of declaration is possible only outside a
function unless it is declared static.
Direct initialization is possible in the following ways:
char strl[7]={‘E’,’X’,’O’,’D’,’U’,’S’,’0’};
char str2[7]={"EXODUS"};
In the first case, individual elements have been moved into the
array. Therefore, it is essential that the string terminator be
specified explicitly. While in the second case, the string
terminator gets attached automatically because a string has
been assigned.
One-Dimensional Arrays (Contd.)

of 31Ver. 1.0
Programming in C
Practice: 3.2
1. Write a function that stores the alphabets A to Z in an array
by applying arithmetic on ASCII codes, given that the ASCII
code of character A is 65. The function should display the
string also.
2. In a file-delete utility program for 256 files the user response
to whether a file is to be deleted or not is to be stored in an
array as Y for yes and N for no for all files. By default the
user response should be N for all files. Write a function that
sets up an array and accepts user-responses.

of 31Ver. 1.0
Programming in C
Solution:
Microsoft Word
Document

of 31Ver. 1.0
Programming in C
Array elements:
Are referenced by using subscripts.
Are integers, therefore array manipulation is possible through
the use of variables.

of 31Ver. 1.0
Programming in C
Practice: 3.3
1. Write a function to convert a character string into
lower-case.
2. Write a function to compare two strings and to print the
larger one. The strings may be compared in terms of ASCII
code of each character in the strings.

of 31Ver. 1.0
Programming in C
Solution:
Microsoft Word
Document

of 31Ver. 1.0
Programming in C
Practice: 3.4
1. Write a function to accept up to 25 numbers and to display
the highest and lowest numbers along with all the numbers.

of 31Ver. 1.0
Programming in C
Solution:
Microsoft Word
Document

of 31Ver. 1.0
Programming in C
Array Addressing:
To arrive at a particular element, the following formula is
applied:
Starting address + ( Offset number * Scaling
factor) of the array
Here,
Scaling factor is the number of bytes of storage space required
by the specific data type.
Offset number * Scaling factor gives the number of bytes
to be added to the starting address of the array to get to a desired
element.

of 31Ver. 1.0
Programming in C
Practice: 3.5
1. Write a program in C to extract a substring from a specified
position containing a specified number of characters from
an input string.

of 31Ver. 1.0
Programming in C
Solution:
Microsoft Word
Document

of 31Ver. 1.0
Programming in C
Multidimensional Arrays
C also supports multidimensional arrays.
A two-dimensional array is the simplest form of the
multidimensional array.
A two-dimensional array is an array of one-dimensional
arrays.
A two-dimensional array is also known as a two-d array.
A two-d array is declared as follows:
type arrayname[Row][Col];
Rules for initializing a two-d array are same as that of a
one-dimensional array.
The row subscript may be left blank for a more flexible
declaration.

of 31Ver. 1.0
Programming in C
Practice: 3.6
1. State whether True or False:
If the number of salesmen is 5, then the declaration of the
two-dimensional array and its initialization to zero would be:
int s_p_array [5][4] = {
{0,0,0,0,0},
{0,0,0,0,0},
{0,0,0,0,0},
{0,0,0,0,0},
};

of 31Ver. 1.0
Programming in C
Solution:
1. False. Note that since there are 5 salesman with 4 products,
there should be 5 sets of {}, each containing four zeroes. The
correct initialization is:
int s_p_array [5][4] = {
{0,0,0,0},
{0,0,0,0},
{0,0,0,0},
{0,0,0,0},
{0,0,0,0},
};

of 31Ver. 1.0
Programming in C
Two-Dimensional Character Arrays:
Are typically used to create an array of strings.
Use two subscripts, one for row and the other for column.
Are declared as:
char err_msg [row] [col];
Can be initialized at the time of declaration.
Multidimensional Arrays (Contd.)

of 31Ver. 1.0
Programming in C
Practice: 3.7
1. Based on the books array, predict the output of the following
commands:
a. printf(“%c”, books[2][5]);
b. printf(“%s”,books[3]);
c. printf(“%d”,books[4][7]);

of 31Ver. 1.0
Programming in C
Solution:
a. M
b. Birds, Beasts, and Relatives
c. 97

of 31Ver. 1.0
Programming in C
Practice: 3.8
1. Write the program segment to calculate the class average
across students in each subject.
2. Assume that the data exists in the arrays and averages
have been calculated. Write program segments, which will
allow the user to query on the arrays to:
a. Display Student Names and Average Marks.
b. Display Subjects and Class Averages.

of 31Ver. 1.0
Programming in C
c. Display Marks of a specific Student in a specific Subject.
d. Display Subject wise marks of all students whose average is
above 80.
For each option the following action needs to be taken.
OPTION ACTION
a. Display each student's name along with his average marks.
b. Display each subject along with class average on the subject.
c. Display list of students and list of subjects. Allow the user to
choose one from each. Based on the numbers chosen, display
the appropriate marks. Remember, subscripting in C starts from
zero.
d. Check the average of each student. Wherever average
exceeds 80, display the student name and the subject name
and marks in each subject.

of 31Ver. 1.0
Programming in C
Solution:
Microsoft Word
Document

of 31Ver. 1.0
Programming in C
Appreciating Preprocessor Directives
Preprocessor directives:
Are instructions to the compiler in the source code of a C
program.
Are not actually a part of the C language.
Expand the scope of the C programming environment.
Begin with a #.
#include is also a preprocessor directive.
#include instructs the compiler to include the specified
source file into the one which contains the #include
directive.
#define defines an identifier and a string constant that will
be substituted for the identifier each time it is encountered in
the file.

of 31Ver. 1.0
Programming in C
Appreciating Preprocessor Directives (Contd.)
It helps in reducing the chances of inconsistency within the
program and also makes the program easy to modify.
Consider the following macro definition:
#define TRUE 1
No semicolon is required after the statement.
Every time the compiler encounters the string TRUE in the
program, it substitutes it with the value 1.
No text substitution will occur if the identifier is enclosed
within quotes.

of 31Ver. 1.0
Programming in C
Summary
In this session, you learned that:
An array can be defined as a contiguous area in memory,
which can be referred to by a common name.
In C, arrays can be categorized as:
One-dimensional/Single-dimensional arrays
Multidimensional arrays
The syntax for declaring a one-dimensional array is as follows:
type arrayname[n];
Array elements are referenced by using subscripts.
The last element in a character array is reserved to store the
string terminator character 0 (NULL).
An array can be initialized, when declared, by specifying the
values of some or all of its elements.
Initialization can also be done inside the function, after the
array has been declared, by accepting the values.

of 31Ver. 1.0
Programming in C
Summary (Contd.)
To arrive at the particular element, the following formula is
applied:
Starting address + ( Offset number * Scaling
factor) of the array
C supports multidimensional arrays.
The simplest form of the multidimensional array is the
two-dimensional (two-d) array.
The general form of declaration of the two-d array would be:
type arrayname[x][y];
Two-dimensional integer arrays are very much like
one-dimensional integer arrays, the only difference being that
two-dimensional arrays have two indices.
Initialization of two-dimensional arrays can be done at the time
of declaration itself.
A better way to initialize a two-dimensional array is using the
for statement.

of 31Ver. 1.0
Programming in C
Summary (Contd.)
Two-dimensional character arrays are declared in the same
way as two-dimensional integer arrays:
The first index specifies the number of strings.
The second index specifies the length of the longest string plus
one.
Initialization can be done along with declaration, if done outside
main().
Preprocessor directives are not actually a part of the C
language; they expand the scope of the C programming
environment.
The preprocessor directives normally begin with a #.
#include is also a preprocessor directive. It instructs the
compiler to include the specified source file into the one which
contains the #include directive.

of 31Ver. 1.0
Programming in C
Summary (Contd.)
The #define statement can be used to declare a variable with
a constant value throughout the program. It helps in:
Reducing the chances of inconsistency within the program.
Making modification easier, as the value has to be changed only
at one place.

C programming session 05

More Related Content

What's hot (20)

Viewers also liked (6)

Similar to C programming session 05 (20)

More from Vivek Singh (20)

Recently uploaded (20)

C programming session 05

Editor's Notes