Lec1_EENG112-Introduction.pdf

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EENG/INFE112: INTRO.TO PROGRAMMING
Introduction to
C Programming
Dr. Hasan Demirel
C How to Program,
H. M. Deitel and P. J. Deitel,
Prentice Hall, 5th edition
(3rd edition or above is also OK).

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Programming Languages
• There are three types of programming Languages
1) Machine Languages (machine codes):
• Strings of 1s and 0s.
• Only unterstood by integrated circuits, such as microprocessors.
Example: 10100010
01011011
10101010
2) Assembly Languages:
• English-like abbreviations representing elementary computer
operations.
• translated to machine code by using assemblers.
Example: MOV AL,3BH
ADD AL, AH
SUB AL,AH
MOV [SI]
 2000 Prentice Hall, Inc. All rights reserved.

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Programming Languages
• There are three types of programming Languages
1) Machine Language
2) Assembly Languages
3) High-level Languages:
• Codes similar to everyday English
• Use mathematical notations
• translated to machine code by using compilers.
• C, C++, PASCAL, FORTRAN, BASIC are high-level languages.
Example:
c=a+b;
if(a<b)
printf(“a is less than bn”);
else
printf(“a is NOT less than bn”);

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Structured programming
• Disciplined approach to writing programs
 Using flowcharts (graphical representation)
 Using pseudocodes or step by step algorithms.
• Clear, easy to test and debug and easy to modify
• Using functions for efficient programming.
Multitasking
Specifying that many activities run in parallel.

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Basics of a Typical C Program Development Process
• Phases of C Programs:
1. Edit
2. Preprocess
3. Compile
4. Link
5. Load
6. Execute
Program is created in
the editor and stored on disk.
Preprocessor program
processes the code.
Loader puts program in
memory.
CPU takes each instruction
and executes it, possibly
storing new data values
as the program executes.
Compiler creates object code
and storesi it on disk.
Linker links the object
code with the libraries
Loader
Primary Memory
Compiler
Editor
Preprocessor
Linker
Primary Memory
.
.
.
.
.
.
.
.
.
.
.
.
Disk
Disk
Disk
CPU
Disk
Disk

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Simple C Program:
/* This is our first program in C Language */
#include <stdio.h>
int main()
{
printf("Hello Worldn");
return 0;
}
• The following program displays "Hello World" on the
computer screen (monitor).
Hello World
• The program output

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Simple C Program:
#include <stdio.h>
int main()
{
return 0;
}
Comments:
• Text surrounded by /* and */ is ignored by computer.
• Used to describe program.
#include <stdio.h>
Preprocessor directive:
• Tells computer to load contents of a header file <stdio.h>,
• which includes standard input/output functions.
• For example printf()is one of the standard input/output functions.

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Simple C Program:
#include <stdio.h>
int main()
{
return 0;
}
int main()
• C programs contain one or more functions,
• One of the functions must be main().
• Parenthesis used to indicate a function
• int means that main "returns" an integer value
• Braces ({ and }) indicate a block
• The bodies of all functions must be contained in braces.

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Simple C Program:
#include <stdio.h>
int main()
{
return 0;
}
• printf()function print the string of characters within quotes (" ")
• All statements must end with a semicolon (;)
• n is the newline character.
return 0;
• A way to exit a function.
• return 0, in this case, means that the program terminated normally.
Right brace }
• Indicates end of main has been reached.

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Simple C Program:
• Example 1: Write a C program which displays your name and
surname in two consecutive lines .
• Example 2: Write a C program which displays the following lines.
Today
is a
nice
day

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C Program: Addition of two integer numbers
/* This program adds two integer numbers */
#include <stdio.h>
int main()
{
int a, b, sum; /* variable declarations */
printf("Enter first integern"); /* prompt the user */
scanf( "%d", &a); /* read first integer */
printf("Enter second integern"); /* prompt the user */
scanf( "%d", &b); /* read second integer */
sum = a + b; /* calculate the sum */
printf( "Sum = %dn", sum ); /* print the calculated sum*/
return 0; /* indicate that program ended successfully */
}
Enter first integer
15
Enter second integer
26
Sum = 41
Program Output

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int a, b, sum;
• Declaration of variables
- Variables: locations in memory where a value can be stored
• int means the variables can hold integer numbers (-1, 3, 0, 47)
• Variable names (identifiers)
- a, b, sum;
- Identifiers: consist of letters, digits (cannot begin with a digit) and
underscores( _ ). They are Case sensitive
• Declarations appear before executable statements
- If an executable statement references and undeclared variable it
will produce a syntax (compiler) error.

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scanf( "%d", &a );
• Obtains(reads/inputs) a value from the user
 scanf uses standard input (usually keyboard)
• This scanf statement has two arguments
%d - indicates data should be a decimal integer
&a – location (address) in memory to store variable a.
& is confusing in beginning – for now, just remember to
include it with the variable name in scanf statements.
• When executing the program the user responds to the scanf statement
by typing in a number, then pressing the enter (return) key.

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= (assignment operator)
• Assigns a value to a variable
• Is a binary operator (has two operands)
sum = a + b;
sum gets a + b;
• Variable receiving value on left
printf( "Sum is %dn", sum );
• Similar to scanf
- %d means decimal integer will be printed
- sum specifies what integer will be printed
• Calculations can be performed inside printf statements
printf( "Sum is %dn", a + b );

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• Example 3: Write a C program which calculates and displays the
addition of integers 7, 8 and 14..
• Example 4: Write a C program which asks the user to enter 3
integer numbers and outputs the sum of these three numbers.

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Arithmetic Operations in C
• Arithmetic Calculations:
- Use * for multiplication and / for division
- Integer division truncates remainder
7 / 5 evaluates to 1
- Modulus operator(%) returns the remainder of modular division.
7 % 5 evaluates to 2
• Operator precedence:
- Some arithmetic operators act before others
(i.e., multiplication before addition)
- Use parenthesis when needed
- Example: Find the average of three variables a, b and c
Do not use: a + b + c / 3
Use: (a + b + c ) / 3

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• Arithmetic operators:
C operation Arithmetic
operator
Algebraic
expression
C expression
Addition + f + 7 f + 7
Subtraction - p – c p - c
Multiplication * bm b * m
Division / x / y x / y
Modulus % r mod s r % s

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• Rules of Operator Presidence:
Operator(s) Operation(s) Order of evaluation (precedence)
() Parentheses Evaluated first. If the parentheses are nested, the
expression in the innermost pair is evaluated first. If there
are several pairs of parentheses “on the same level” (i.e.,
not nested), they are evaluated left to right.
*, /, or % Multiplication,Divi
sion, Modulus
Evaluated second. If there are several, they are
evaluated left to right.
+ or - Addition
Subtraction
Evaluated last. If there are several, they are
evaluated left to right.

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Decision Making: Equality and Relational Operators
• Executable statements
– Perform actions (calculations, input/output of data)
– Perform decisions
 May want to print "pass" or "fail" given the value of a
test grade
• if control structure
– Simple version in this section, more detail later
– If a condition is true, then the body of the if statement
executed
 0 is false, non-zero is true
– Control always resumes after the if structure
• Keywords
– Special words reserved for C
– Cannot be used as identifiers or variable names

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Standard algebraic
equality operator or
relational operator
C equality or
relational
operator
Example of C
condition
Meaning of C
condition
Equality Operators
= == x == y x is equal to y
not = != x != y x is not equal to y
Relational Operators
> > x > y x is greater than y
< < x < y x is less than y
>= >= x >= y x is greater than or
equal to y
<= <= x <= y x is less than or
equal to y

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Keywords
auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

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1 /* Fig. 2.13: fig02_13.c
2 Using if statements, relational
3 operators, and equality operators */
4 #include <stdio.h>
5
6 int main()
7 {
8 int num1, num2;
9
10 printf( "Enter two integers, and I will tell youn"
);
11 printf( "the relationships they satisfy: " );
12 scanf( "%d%d", &num1, &num2 ); /* read two
integers */
13
14 if ( num1 == num2 )
15 printf( "%d is equal to %dn", num1, num2 );
16
17 if ( num1 != num2 )
18 printf( "%d is not equal to %dn", num1, num2 );
19
20 if ( num1 < num2 )
21 printf( "%d is less than %dn", num1, num2 );
22
23 if ( num1 > num2 )
24 printf( "%d is greater than %dn", num1, num2 );
25
26 if ( num1 <= num2 )
27 printf( "%d is less than or equal to %dn",
28 num1, num2 );
Program Outline
1. Declare variables
2. Input
2.1 if statements
3. Print

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Program Outline
3.1 Exit main
Program Output
29
30 if ( num1 >= num2 )
31 printf( "%d is greater than or equal to %dn",
32 num1, num2 );
33
34 return 0; /* indicate program ended successfully */
35 }
Enter two integers, and I will tell you
the relationships they satisfy: 3 7
3 is not equal to 7
3 is less than 7
3 is less than or equal to 7
Enter two integers, and I will tell you
the relationships they satisfy: 22 12
22 is not equal to 12
22 is greater than 12
22 is greater than or equal to 12

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• Example 5: Write a C program which asks the user to enter two
integers, compare them and perform the following actions:
- if the first value is greater -> add the two numbers,
- if the second value is greater -> multiply the integers
- if they are equal -> divide their multiplication with their sum.

Lec1_EENG112-Introduction.pdf

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