Introduction to Basic C programming 01

Introduction to C
Workshop India
Wilson Wingston Sharon
wingston.sharon@gmail.com

Writing the first program
#include<stdio.h>
int main()
{
printf(“Hello”);
return 0;
}

 This program prints Hello on the screen when we
execute it

Header files
 The files that are specified in the include section is
called 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

Main function

 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

Comments in C
 Single line comment
 // (double slash)
 Termination of comment is by pressing enter key

 Multi line comment
/*….
…….*/
This can span over to multiple lines

Data types in C
 Primitive data types
 int, float, double, char
 Aggregate data types
 Arrays come under this category
 Arrays can contain collection of int or float or char or
double data
 User defined data types
 Structures and enum fall under this category.

Variables
 Variables are data that will keep on changing
 Declaration
<<Data type>> <<variable name>>;
int a;
 Definition
<<varname>>=<<value>>;
a=10;
 Usage
<<varname>>
a=a+1; //increments the value of a by 1

Operators

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

Variable names- Rules
 Should not be a reserved word like int 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.

Input and Output
 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

Task01- I/O
Write a program to accept 3 numbers a , b and c as
coefficients of the quadratic equation
ax2 + bx + c = 0
And output the solution.

Hint:
6.There will be two answers for every input combination.

7.Look in a math textbook for the solution formula.

For loops
 The syntax of for loop is
for(initialisation;condition checking;increment)
{
set of statements
}
Eg: Program to print Hello 10 times
for(I=0;I<10;I++)
{
printf(“Hello”);
}

While loop
 The syntax for while loop
while(condn)
{
statements;
}
Eg:
a=10;
while(a != 0) Output: 10987654321
{
printf(“%d”,a);
a--;
}

Do While loop
 The syntax of do while loop
do
{
set of statements
}while(condn);

Eg:
i=10; Output:
do 10987654321
{
printf(“%d”,i);
i--;
}while(i!=0)

Task02 - loops
 Write a program to identify which day ( sat – fri) a
particular given date (e.g. : 3/3/2015) falls upon.

 Hint:
http://en.wikipedia.org/wiki/Zeller%27s_congruence

 Read through the algorithm and implement it.
 You can make your own algorithm and get bonus
marks.

Conditional statements
if (condition)
{
stmt 1; //Executes if Condition is true
}
else
{
stmt 2; //Executes if condition is false
}

Conditional statement

switch(var)
{
case 1: //if var=1 this case executes
stmt;
break;
case 2: //if var=2 this case executes
stmt;
break;
default: //if var is something else this will execute
stmt;
}

Functions and Parameters
 Syntax of function
Declaration section
<<Returntype>> funname(parameter list);
Definition section
<<Returntype>> funname(parameter list)
{
body of the function
}
Function Call
Funname(parameter);

Example function
#include<stdio.h>
void fun(int a); //declaration
int main()
{
fun(10); //Call
}
void fun(int x) //definition
{
printf(“%d”,x);
}

Task03 - Primality
 Write a function to check if a given number is prime
or not.

 http://en.wikipedia.org/wiki/Prime_number

 Try and implement at least 2 algorithms and check
which one returns faster.
 Use this for time stamping :
http://www.chemie.fu-berlin.de/chemnet/use/info/libc/

Arrays
 Arrays fall under aggregate data type
 Aggregate – More than 1
 Arrays are collection of data that belong to same
data type
 Arrays are collection of homogeneous data
 Array elements can be accessed by its position in
the array called as index

Arrays
 Array index starts with zero
 The last index in an array is num – 1 where num is the
no of elements in a array
 int a[5] is an array that stores 5 integers
 a[0] is the first element where as a[4] is the fifth
element
 We can also have arrays with more than one
dimension
 float a[5][5] is a two dimensional array. It can store
5x5 = 25 floating point numbers
 The bounds are a[0][0] to a[4][4]

Task04 - Arrays
Produce a spiral array. A spiral array is a square arrangement
of the first N2 natural numbers, where the numbers increase
sequentially as you go around the edges of the array spiralling
inwards.
For example, given 5, produce this array:

0 1 2 3 4
15 16 17 18 5
14 23 24 19 6
13 22 21 20 7
12 11 10 9 8

Introduction to Basic C programming 01

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