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Unit No-2
Basics of C Programming
2.1 Introduction to C.
2.2 Data Concepts.
2.3 Basic Input Output.

2.1 Introduction to C
• History of C.
• General Structure of C program.
• Header files.
• Main Function.

History of C Language
•  Developed at AT&T’s Bell Laboratories of USA in 1972
•  Designed and written by a man named Dennis Ritchie
•  Most of its principles and ideas were taken from the earlier
language B, BCPL and CPL
•  Languages before C are PL/I, ALGOL, FORTRAN, Pascal,
APL, B

Unit No 2.pptx Basic s of C Programming

Importance of C
•  General purpose language but normally used for system
programming
•  Robust due to rich set of built in functions and operaters for
writing complex program
•  C is highly portable i.e. platform independent
•  Can add our own functions to C library

Structure of C program.
• A C program is divided into different
sections. There are six main sections
to a basic c program.
The six sections are,
• Documentation
• Link
• Definition
• Global Declarations
• Main functions
• Subprograms

Documentation Section
• The documentation section is the part of the program where the programmer
gives the details associated with the program. He usually gives the name of the
program, the details of the author and other details like the time of coding and
description. It gives anyone reading the code the overview of the code.
• Example
/* File Name: Helloworld.c
Author: om Sai
date: 09/08/2021
*/

Link Section
• This part of the code is used to declare all the header files that will be used in the program. This leads to the compiler
being told to link the header files to the system libraries.
• Example
• #include<stdio.h>
Definition Section
• In this section, we define different constants. The keyword define is used in this part.
• #define PI=3.14
Global Declaration Section
• This part of the code is the part where the global variables are declared. All the global variable used are declared in this
part. The user-defined functions are also declared in this part of the code.
float b;
int a=7;

Main Function Section
Every C-programs needs to have the main function. Each main function contains 2 parts. A declaration
part and an Execution part. The declaration part is the part where all the variables are declared. The execution part
begins with the curly brackets and ends with the curly close bracket. Both the declaration and execution part are
inside the curly braces.
int main(void)
{
int a=10;
printf(" %d", a);
return 0;
}
Sub Program Section
All the user-defined functions are defined in this section of the program.
int add(int a, int b)
{
return a+b;
}

Header Files
In C language, header files contain the set of predefined standard library functions. The “#include” preprocessing
directive is used to include the header files with “.h” extension in the program.
• Here is the table that displays some of the header files in C language,
Header Files Description
1. stdio.h Input/Output functions
2. conio.h Console Input/Output functions
3. stdlib.h General utility functions
4. math.h Mathematics functions
5. string.h String functions
6. ctype.h Character handling functions
7. time.h Date and time functions
8. float.h Limits of float types
9. limits.h Size of basic types
10.wctype.h Functions to determine the type contained in wide character data.

2.2 Data Concepts
• Character Set
• Tokens
• Keywords
• Identifires
• Variables
• Constants
• Datatypes
• C Operators
• Arithmetic Operators

C CharacterSet
• A character denotes any alphabet, digit or special symbol used
to represent information.
• Alphabets A,B,…..,Y,Z a,b,……,y,z
• Digits 0,1,2, 3,4,5,6, 7,8,9
• Specialsymbols ~‘!@#%^&*()_-+=| {} [ ]:; "'<>,.?/

Tokens
• Smallest individual units are known as C tokens.
• Six Types are
1. Keywords:- float, int, while
2. Identifiers: - name of variables and functions
3. Constants: -15.5, 10
4. Strings: - “Abc”, “year”
5. Special Symbols: - {}, @,
6. Operators: - +,-,*,/

Keywords
• Keywords are the words whose
meaning has already been explained to
the C compiler.
• The following names are reserved by
the C language. Their meaning is
already defined, and they cannot be re-
defined.

• Identifiers refer to the names of variables, functions and arrays, these are user-
defined names
• Constants fixed values that do not change during the execution of a program.
• Variables is a data name that used to store a data value. Value stored in a
variable may change during program execution.
• Data types
•  The datatype determines what kinds of values a variable can store and what
kind of operations can be performed on variables.
• Every variable used in a program must have a data type
• Two types of data types Primary and Secondary
1.  Primary Data Types : - integer, float, character
2.  Secondary Data Types :- array, pointer, structure

C Operators
1.  Arithmetic
2.  Logical
3. Assignment 
4. Relational
5. Increment And Decrement 
6. Conditional 
7. Bit Wise
8. Special
Arithmetic Operators
The basic operators for performing arithmetic:
9. + addition
10.- subtraction
11.* multiplication
12. / division
13.% modulus (remainder)

Declaring Variable
Variable Declaration
•  Every variable in C must be declared before using it in program
•  Variables are declared at the start of body of function of main function
•  Declaration tells the compiler what the variable name is.
•  It specifies what type of data value the variable will hold and what kind of operations can be
– performed on variables.
•  The syntax is : - data_typename_of_variable
•  E.g. int number, amount, balance; for declaring integer type variables
•  E.g. float percent; for declaring float type variables
•  E.g. char grade; for declaring char type variables
Variable Initialization :- Means assigning an initial value to variable.
 
E.g. int num = 1 ; // Variable Declaration and Initialization
Declaring Variable as Constants (const):- E.g. const int class_size = 40;

•  keeps value of variable constant throughout program

2.3 Basic Input Output.
• Input and Output Statements using printf() and scanf().

printf( )
Printf() is used to print only messege or values of variables.General form of printf( ) function is,
printf ( "format string", list of variables ) ; 
• %f for printing real values
• %d for printing integer values
• %c for printing character values
• printf( ) can not only print values of variables, it can also print the result of an expression
• e.g. to print welcome messege the printf() statements is as follows.
printf(“Welcome to Sanjivani KBP Polytechnic”);

scanf()
•  scanf( ) allows us to enter data from keyboard that will be formatted in a certain way.
•  The general form of scanf( ) statement is as follows:
• scanf ( "format string", list of addresses of variables ) ;
• For example:
• scanf ( "%d ", &c ) ;
– Addresses of variables (addresses are obtained by using ‘&’ the ‘address of’ operator) is send to scanf( ) function. This is
necessary because the values received from keyboard must be dropped into variables corresponding to these addresses.
The values that are supplied through the keyboard must be separated by either blank(s), tab(s), or newline(s).
• The ampersand (&) before the variables in the scanf( ) function is a must. & is an ‘Address of’
operator. It gives the location number used by the variable in memory. When we say &a, we are
telling scanf( ) at which memory location should it store the value supplied by the user from the
keyboard.

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Unit No 2.pptx Basic s of C Programming

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