C Program

Professor Dr. M. Ismail Jabiullah

Professor
Department of CSE
Daffodil International University
Bangladesh
 C Program

Basic Program Structures and Variables

 C Program Structure
 Data Types
 Concept of Variables
 Variable Naming Conventions
 C Reserve Words
 Introduction
 The C programming language was designed by Dennis Ritchie at Bell
Laboratories in the early 1970s

Influenced by
 ALGOL 60 (1960),
 CPL (Cambridge, 1963),
 BCPL (Martin Richard, 1967),
 B (Ken Thompson, 1970)

 Traditionally used for systems programming, though this may be changing

in favor of C++

 Traditional C:
 The C Programming Language, by Brian Kernighan and Dennis Ritchie,
2nd Edition, Prentice Hall
 Referred to as K&R
 Standard C
 Standardized in 1989 by ANSI (American National Standards Institute)
known as ANSI C
 International standard (ISO) in 1990 which was adopted by ANSI and is
known as C89
 As part of the normal evolution process the standard was updated in 1995
(C95) and 1999 (C99)
 C++ and C
• C++ extends C to include support for Object Oriented
Programming and other features that facilitate large
software development projects
• C is not strictly a subset of C++, but it is possible to write “Clean C”
that conforms to both the C++ and C standards.

c
 Elements of a C Program
 A C development environment includes
 System libraries and headers: a set of standard libraries and their header
files. For example see /usr/include and glibc.
 Application Source: application source and header files
 Compiler: converts source to object code for a specific platform
 Linker: resolves external references and produces the executable module
 User program structure
 There must be one main function where execution begins when the program
is run. This function is called main
 int main (void) { ... },
 int main (int argc, char *argv[]) { ... }
 int main (int argc, char *argv[], char *envp[])
 additional local and external functions and variables
 C Program Structure
 C programs are composed of one or more functions and at least one function must have
name main().
 If there is only one function and that should be main().
 C program start its execution from the function main().
 Function must have
 Function heading with () symbol and all arguments are in the brackets ()
 Arguments must have declared before use
 Function have all of its actions in the function body.

/*program to calculate the sum of two integer numbers*/ Comment

#include <stdio.h> Header file preprocess
void main() Function heading
{ Function start
int a, b, s; Variable declaration
printf(“\nEnter First Number: ”); Message display
scanf(“%d”,&a); variable input
printf(“\nEnter Second Number: ”);
scanf(“%d”,&b);
s=a+b; Value of expression assign
printf(“\nSum = %d”,s); Output of the value of variable
} Function end
 Characters in C
C programs consist of
 Constants
 Variables
 Operators
 Expressions

All C fundamental components are written as by

 English Capital letters: A to Z
 English small letters: a to z
 Numerals : 0 to 9
 And special characters in the keyboard: !, *, @, #, $, %, &, (, ), {, }, \,
/, ?, <, >, =, etc.
 C Reserve Words
C programs have some reserved words or keywords and they are:

auto break case char const continue default

do double else enum extern float for
goto if int long register return short
signed sizeof static switch typedef union unsigned
void volatile while
 Identifiers
Identifier
• Identifiers are the names of variables, function names, array names, program
names etc.
• Rules of naming Identifiers
• English characters a to z, 0 to 9, and underscore (_) sign
• First letter must be letter a to z
• No blank space should be allowed within the name
• Maximum 31 characters are allowed.

• Examples:
• a7, sum, average, product, quotient,
increment, for9

are valid identifiers.

 2sum, totalsum’s, sum-1, average 8,

product?, const, switch

are not valid identifiers.

 Identifiers (Exercise)
Identify the Valid Identifiers (with Explanation)
1. Aaaaaa7
2. add7sum
3. findaverage
4. 9product
5. 109quotient
6. increment_decrement
7. for999
8. valid-identifiers
9. 2*sum
10. Total=sum’s
11. sum-165
12. average 8
13. product?7
14. Const
15. notvalididentifiers
 Data Types in C
C has several data types and they are:
 Integer
 Character
 Floating-point numbers
 Double-precision Numbers

All data types have four modifiers and they are:

 signed
 unsigned
 long
 short
 Data Ranges of Each Data Types in C
Data Type Data Type Description Memory Size
char Character Types 1 byte
int Integer Type Numbers 2 bytes or 1 word
float Floating-point Numbers 4 bytes or 2 words
double Double-Precision Numbers 8 bytes or 4 words

Data Type Size of Memory Memory Range

char 1 byte -128 to +127
signed char 1 byte -128 to +127
unsigned char 1 byte 0 to 255
int 2 bytes -32768 to +32767
signed int 2 bytes -32768 to +32767
unsigned int 2 bytes 0 to 65535
short in 2 bytes -32768 to +32767
long int 4 bytes -2147483648 to +2147483647
unsigned long int 4 bytes 0 to 4294967295
 Constants
Constants in C are 4 kinds:
 Integer Constants
 Character Constants
 Floating-point Constants
 String Constants

 Integer Constants
 No comma, no blank space are in the numbers
 Only negative sign (-) can be place in front of the
constant
 Value must be within the defined upper and lower value

 Examples: 0 1 743 54456 876549

are valid integer constants.
 01 12 3 +345 99999999
are not valid integer constants
 Integer Constants (Exercise)
1. 01987
2. 1,7433
3. 544516
4. 876549
5. 01111
6. 12 35678
7. +1111345
8. 99999999
9. 10,000,000
10. -19098
11. 1908887
12. 3290000.00
 Character Constants
Constants in C are 4 kinds:
 Integer Constants
 Character Constants
 Floating-point Constants
 String Constants
 Character Constants
 A single character or symbol within a single quotation
marks

 Examples: ‘a’ ‘1’ ‘&’ ‘@’ ‘ ‘ are valid integer

constants.
 a’ ‘11’ ‘&6’ ‘@ “ “ are not valid integer
constants.
 Character Constants (Exercise)
1. ‘ab’
2. ‘7’
3. “&’
4. ‘%’
5. ‘“
6. a’
7. ’1981’
8. ‘&6’
9. ‘@
10. ““
11. ‘w’
12. ‘0’
13. ‘-’
14. “0”
 Floating-point Constants
Constants in C are 4 kinds:
 Integer Constants
 Character Constants
 Floating-point Constants
 String Constants
 Floating-point Constants
 All number with decimal point (.) are floating-point numbers
 No comma, no blank space are in the numbers
 Only negative sign (-) can be place in front of the constant
 Value must be within the defined upper and lower value

 Examples: 0. 0.8 873.22 2E-6 0.6E-3 are valid

floating-point numbers

 0 .8 33556677873.22 2E-16 0.6E-0.3 are

not valid floating-point numbers
 Floating-point Constants (Exercise)
1. 19800.
2. 23450.8
3. 12873.220000
4. 209E-6
5. 120.6E-3
6. 0
7. .8
8. 12333556677873.22
9. 2E-16
10. 0.6E-0.3
11. E+123
12. 99999.9999
13. 018978.20
14. 20.018978
 String Constants
Constants in C are 4 kinds:
 Integer Constants
 Character Constants
 Floating-point Constants
 String Constants

 String Constants
 Texts or numbers written within the double quotation sign (“) pair.

 Examples: “jamal” “yellow” “” “123”

are valid string constants

 `jamal` yellow” “Jamal ‘123”

are not valid string constants

 String Constants (Exercise)
1. “jamal’
2. “redyellow”
3. “------ ”
4. “1234567890”
5. `jamal`
6. Yellow”
7. “Jamal
8. ‘123”
9. “Jamal Uddin Russel of CSE Department”
10. ‘Daffodil International University’
11. “Daffodil; International; University”
 Escape Sequences

A character written in within double quotation mark (“”) and

using a slash sign (\) is called escape sequences.

Escape Sequence Equal ASCII Value Functions

\a 007 Ring a alert bell

\b 008 Back Space
\t 009 Tab key
\n 010 New line
\” 034 Double Quotation mark
\’ 039 Single Quotation Mark
\\ 092 Back slash mark
\? 063 Quotient Mark
 C Variables
• Variable is a name that contains the value of the data item.
• Variables contains the value as of its data types.
• Variables must be declared before of its use.
Rules of Variable Names:
• English characters a to z, 0 to 9, and underscore (_) sign
• First letter must be letter a to z
• No blank space should be allowed within the name
• Maximum 31 characters are allowed.
• Examples:
• a7, sum, average, product, quotient,
increment, for9 are valid variable names.

 2sum, totalsum’s, sum-1, average 8,

product?, const, switch are not valid variables.
Examples:
char z, w;
float i, j, l;
int x, y, z, w;
 C Variables (Exercise)
1. A7
2. Sum
3. Average
4. Product
5. Quotient
6. increment
7. 2sum
8. totalsum’s
9. sum-1
10. average 8
11. Product?
12. Const
13. char
14. Z
15. W\
16. Float
17. j
18. L
19. x
20. y
21. z
22. w
 C Expressions
C expressions are of the following types:

Expression or assignment statement:

a = 32;
c = a+b;
++i; or i=i+1;

Compound Statement:
{
int a,b,x;
a=32;
b=43;
x=a+b;
printf(“\nSum = %d”, x);
}
Some C Programs
 1. C Programs
Problem: A C Program to display the name address with a message.
/*program 01: to display the name and address*/
#include<stdio.h>
int main()
{
printf("Jamal Uddin Russel\n");
printf("Department of Computer Science and Engineering\n");
printf("Daffodil International University\n");
printf("Bangladesh\n");
printf("Programming is fun\n");
printf("Welcome to Programming World\n");
return 0;
}
 2. C Programs
Problem: A C program that finds the sum, subtract and product of two
given numbers.
/*program 02: to find the sum, subtract, product of given two numbers*/
#include<stdio.h>
int main()
{
int i,j,sum,subtract,product;
i=250;
j=100;
sum=i+j;
subtract=i-j;
product=i*j;
printf("\n\nSum = %d",sum);
printf("\n\nSubtract = %d",subtract);
printf("\n\nProduct = %d",product);
return 0;
}
 3. C Programs
Problem: A C program that enters two numbers from the keyboard and
finds the sum, subtract and product of them
/*program 03: to find the sum, subtract, product of two numbers where numbers are
inputted from the keyboard*/
#include<stdio.h>
int main()
{
int i,j,sum,subtract,product;
printf("\nEnter first number: ");
scanf("%d",&i);
printf("\nEnter second number: ");
scanf("%d",&j);
sum=i+j;
subtract=i-j;
product=i*j;
printf("\n\nSum = %d",sum);
printf("\n\nSubtract = %d",subtract);
printf("\n\nProduct = %d",product);
return 0;
}
 4. C Programs
Problem: A C program that enters two numbers from the keyboard and
finds the sum, subtract and product of them with formatted output.
/*program 04: to find the sum, subtract, product of given two numbers where numbers
are inputted from the keyboard*/
#include<stdio.h>
int main()
{
int i,j,sum,subtract,product;
printf("\nEnter first number: ");
scanf("%d",&i);
printf("\nEnter second number: ");
scanf("%d",&j);
sum=i+j;
subtract=i-j;
product=i*j;
printf("\n\nSum of %d and %d is = %d",i,j,sum);
printf("\n\nSubtract of %d and %d is = %d",i,j,subtract);
printf("\n\nProduct of %d and %d is = %d",i,j,product);
return 0;
}
More Programs
Program 1: A C program that display the following message
Programming is fun
C programming is also very fun
Welcome to the World of C

/*program 1 to display the following message:

Programming is fun
C programming is also very fun
Welcome to the World of C */
#include<stdio.h>
void main()
{
printf(“Programming is fun");
printf(“C Programming is also very fun”);
printf(“Welcome to the world of C”);
}
Program 2: A C program that display the following message as formatted

Programming is fun
C programming is also very fun
Welcome to the World of C

/*program 2 to display the following message as formatted

Programming is fun
C programming is also very fun
Welcome to the World of C */
#include<stdio.h>
void main()
{
printf(“\nProgramming is fun");
printf(“\nC Programming is also very fun”);
printf(“\nWelcome to the world of C”);
}
Program 03: A C program that finds the sum of two given integer values.

/*program 03 to display the sum*/

#include<stdio.h>
void main()
{
int a,b,s;
a=120, b=210;
printf("Sum = %d",s);
}
 Program 04 : A C program that display the sum of two given integer
values with the given values

/*program 4 to display the sum and the numbers*/

#include<stdio.h>
void main()
{
int a,b,s;
a=120, b=210;
printf("a = %d",a);
printf("b = %d",b);
printf("Sum = %d",s);
}
Program 5: A C program to display the sum and the numbers with proper format

/*program 5 to display the sum and the numbers with proper format*/
#include<stdio.h>
void main()
{
int a,b,s;
a=120, b=210;
printf("\na = %d",a);
printf("\nb = %d",b);
printf("\nSum = %d",s);
}
Program 6: A C program to display the sum of two numbers with the two
numbers as specified format

/*program 6 to display the sum of two numbers with the two numbers as specified
format*/
#include<stdio.h>
void main()
{
int a,b,s;
a=120, b=210;
s=a+b;
printf("\nFirst Number = %d",a);
printf("\nSecond Number = %d",b);
printf("\nSum = %d",s);
}
Program 7: A C Program that display the sum, subtract and product with
the given numbers and specified format

/*program 7 to display the sum, subtract, product with the format*/

#include<stdio.h>
void main()
{
int a,b,s,sb,pr;
a=120, b=210;
s=a+b;
sb=a-b;
pr=a*b;
printf("\nFirst Number = %d",a);
printf("\nSecond Number = %d",b);
printf("\nSum = %d",s);
printf("\nSubtract = %d",sb);
printf("\nProduct = %d",pr);
}
Program 8: A C Program that display the sum, subtract and product with
the numbers taken from the keyboard and specified format

/*program 8 to display the sum, subtract, product of the two numbers taken from
the keyboard with the format*/
#include<stdio.h>
void main()
{
int a,b,s,sb,pr;
printf("\nEnter First Number = %d",a);
scanf(“%d”,&a);
printf("\nSecond Number = %d",b);
scanf(“%d”,&b);
s=a+b;
sb=a-b;
pr=a*b;
printf("\nFirst Number = %d",a);
printf("\nSecond Number = %d",b);
printf("\nSum = %d",s);
printf("\nSubtract = %d",sb);
printf("\nProduct = %d",pr);
}
Thanks