This document provides an overview of the C programming language, covering topics such as the basic structure and skeleton of a C program, header files, the main function, running and compiling a C program, comments, variables, data types, constants, input/output operations and functions, programming errors, and keywords. It discusses the basic building blocks of a C program and how it is compiled and run, as well as fundamental concepts like variables, data types, operators, and functions.

2. • OVERVIEW OF C
• C PROGRAM SKELETON
• C PROGRAM STRUCTURE
• HEADER FILES
• MAIN FUNCTION
• RUNNING A C PROGRAM
• COMMANDS IN C
• VARIABLE NAME RULES
• INPUT/OUTPUT
• OPERATORS
• CHARACTERS USED IN C

3. • SPECIAL CHARACTERS
• KEYWORDS
• IDENTIFIERS
• ESCAPE SEQUENCE
• VARIABLES
• BASIC DATA TYPES
• CONSTANTS
• I/O OPERATIONS
• I/O FUNCTIONS
• PROGRAMMING ERRORS
• NOTES
• BIBLIOGRAPHY
• END PAGE

4. • C is developed by Dennis Ritchie
• C is a structured programming language
• C supports functions that enables easy
maintainability of code, by breaking large file
into smaller modules
• Comments in C provides easy readability
• C is a powerful language

5. • In short, the basic skeleton of a C program
looks like this:
#include <stdio.h>
void main()
{
statement(s);
}
Preprocessor directives
Main function
Start of
segment(program)
End of
segment(program)

6. Simple C Program
#include<stdio.h>
void main()
{
--other statements
// Comments after double slash
}

7. • The files that are specified in the include
section are known as header file
• These are precompiled files that has some
functions defined in them
• We can call those functions in our program
by supplying parameters
• Header file is given an extension .h
• C Source file is given an extension .c

8. • This is the entry point of a program
• When a file is executed, the start point is the
main function
• From main function the flow goes as per the
programmers choice.
• There may or may not be other functions
written by user in a program
• Main function is compulsory for any c program

9. • Type a program
• Save it
• Compile the program – This will generate an exe file
(executable)
• Run the program (Actually the exe created out of
compilation will run and not the .c file)
• In different compiler we have different option for
compiling and running. We give only the concepts.

10. • Single line comment
– // (double slash)
– Termination of comment is by pressing enter key
• Multi line comment
/*….
…….*/
This can span over to multiple lines

11. • Should not be a reserved word like int,struct
etc..
• Should start with a letter or an underscore(_)
• Can contain letters, numbers or underscore.
• No other special characters are allowed
including space
• Variable names are case sensitive
– A and a are different.

12. • Input
– scanf(“%d”,&a);
– Gets an integer value from the user and stores it
under the name “a”
• Output
– printf(“%d”,a);
– Prints the value present in variable a on the
screen

13. • Arithmetic (+,-,*,/,%)
• Relational (<,>,<=,>=,==,!=)
• Logical (&&,||,!)
• Bitwise (&,|)
• Assignment (=)
• Compound assignment(+=,*=,-=,/=,%=,&=,|=)
• Shift (right shift >>, left shift <<)

16. C language uses the following keywords which are not available to users to
use them as variables/function names. Keywords are always written with
the lower case letters. Some C compilers use more keywords which they
include in their documentation or manual pages.

17. An identifier is a name having a few letters , numbers and special character
_(underscore). It is used to identify a variable, function, symbolic constant
and so on. An identifier can be written with a maximum of 31 characters.
Example:
x2 , sum ,avg (can be used as variables)
calcu_avg , matadd (can be used as function names)
pi, sigma (can be used as symbolic constants)

19. Escape Sequence Effect
a Beep sound
b Backspace
f Formfeed (for printing)
n New line
r Carriage return
t Tab
v Vertical tab
Backslash
” “ sign
o Octal decimal
x Hexadecimal
O NULL

20. • Variable  a name associated with a memory
cell whose value can be change
• Variable Declaration: specifies the type of a
variable
– Example: int num;
• Variable Definition: assigning a value to the
declared variable
– Example: num = 5;

21. • There are 4 basic data types :
– int
– float
– double
– char
• int
– used to declare numeric program variables of integer type
– whole numbers, positive and negative
– keyword: int
int number;
number = 12;

22. • float
– fractional parts, positive and negative
– keyword: float
float height;
height = 1.72;
• double
– used to declare floating point variable of higher precision
or higher range of numbers
– exponential numbers, positive and negative
– keyword: double
double valuebig;
valuebig = 12E-3;

23. • char
– equivalent to ‘letters’ in English language
– Example of characters:
• Numeric digits: 0 - 9
• Lowercase/uppercase letters: a - z and A - Z
• Space (blank)
• Special characters: , . ; ? “ / ( ) [ ] { } * & % ^ < > etc
– single character
– keyword: char
char my_letter;
my_letter = 'U';
• In addition, there are void, short, long, etc.

24. • Entities that appear in the program code as fixed values.
• Any attempt to modify a CONSTANT will result in error.
• 3 types of constants:
– Integer constants
• Positive or negative whole numbers with no fractional part
• Example:
– const int MAX_NUM = 10;
– const int MIN_NUM = -90;
– Floating-point constants (float or double)
• Positive or negative decimal numbers with an integer part, a
decimal point and a fractional part
• Example:
– const double VAL = 0.5877e2; (stands for 0.5877 x
102)

25. – Character constants
• A character enclosed in a single quotation mark
• Example:
– const char letter = ‘n’;
– const char number = ‘1’;
– printf(“%c”, ‘S’);
» Output would be: S

26. #include <stdio.h>
void main()
{
const double pi = 3.412; //hence pi value cant be changed
double h, r, b, volume;
printf(“Enter the height and radius of the cone:”);
scanf(“%lf %lf”,&h, &r);
b = pi * r * r;
volume = (1.0/3.0) * b * h;
printf(“nThe volume of a cone is :%f ”, volume);
}

27. • Input operation
– an instruction that copies data from an input
device into memory
• Output operation
– an instruction that displays information stored in
memory to the output devices (such as the
monitor screen)

28. • A C function that performs an input or output
operation
• A few functions that are pre-defined in the
header file stdio.h such as :
– printf()
– scanf()
– getchar() & putchar()
– gets() & puts()

29. • Used to send data to the standard output (usually
the monitor) to be printed according to specific
format.
• General format:
– printf(“string literal”);
• A sequence of any number of characters surrounded by
double quotation marks.
– printf(“format string”, variables);
• Format string is a combination of text, conversion
specifier and escape sequence.

30. • Example:
– printf(“Thank you”);
– printf (“Total sum is: %dn”, sum);
• %d is a placeholder (conversion specifier)
– marks the display position for a type integer variable
• n is an escape sequence
– moves the cursor to the new line

31. • Read data from the standard input device
(usually keyboard) and store it in a variable.
• General format:
– scanf(“Format string”, &variable);
• Notice ampersand (&) operator :
– C address of operator
– it passes the address of the variable instead of the
variable itself
– tells the scanf() where to find the variable to store
the new value

32. • Example :
int age;
printf(“Enter your age: “);
scanf(“%d”, &age);
• Common Conversion Identifier used in printf and
scanf functions.

33. • Debugging  Process removing errors from a
program
• Three kinds of errors :
– Syntax Error
• a violation of the C grammar rules, detected during
program translation (compilation).
• statement cannot be translated and program
cannot be executed

34. – Run-time errors
• An attempt to perform an invalid operation,
detected during program execution.
• Occurs when the program directs the computer to
perform an illegal operation, such as dividing a
number by zero.
• The computer will stop executing the program, and
displays a diagnostic message indicates the line
where the error was detected

35. – Logic Error/Design Error
• An error caused by following an incorrect algorithm
• Very difficult to detect - it does not cause run-time
error and does not display message errors.
• The only sign of logic error – incorrect program output
• Can be detected by testing the program thoroughly,
comparing its output to calculated results
• To prevent – carefully desk checking the algorithm and
written program before you actually type it

36. • C is case-sensitive
– Word, word, WorD, WORD, WOrD, worD, etc are all different
variables / expressions
Eg. sum = 23 + 7
• Comments
– are inserted into the code using /* to start and */ to end a
comment
– Some compiler supports comments starting with ‘//’
– Provides supplementary information but is ignored by the
preprocessor and compiler
• /* This is a comment */
• // This program was written by Hanly Koffman

37. • Reserved Words
– Keywords that identify language entities such as
statements, data types, language attributes, etc.
– Have special meaning to the compiler, cannot be
used as identifiers (variable, function name) in our
program.
– Should be typed in lowercase.
– Example: const, double, int, main, void,printf,
while, for, else (etc..)

38. • Punctuators (separators)
– Symbols used to separate different parts of the C
program.
– These punctuators include:
[ ] ( ) { } , ; “: * #
– Usage example:

39. • Operators
– Tokens that result in some kind of computation or
action when applied to variables or other
elements in an expression.
– Example of operators:
• * + = - /
– Usage example:
• result = total1 + total2;

40. • Google
• Wikipedia
• Reference books