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Programming Basics
Introduction to C programming

How does a program run?
● Step 1 → Write lines of codes.
● Step 2 → Compile.
● Step 3 → Execute.
● Step 4 → Get the output.

IDE vs Compiler
● IDE – Integrated Development Environment
● Compiler → translates to machine level(01010)

Hello World in Detail :
● stdio.h is a header file
● #include is a preprocessor directive.
● int main() : where the program execution
begins.
● { and } symbols mark the beginning and end of
a block of code.
● return 0; terminates the main() function

Identifiers
● name given to entities such as variables,
functions.
● Example - int money ;
● int money;
Here, money is identifier.
● must be different from keywords

Keywords
● predefined, reserved words.
● Example : int money;
int is a keyword .

Variable
● a variable is a container to hold data.
● Example: int score = 95;

Rules for naming a variable
● can have letters , digits and underscore only.
● The first letter of a variable should be either a
letter or an underscore

Integer
● positive and negative values but no decimal
values. Eg : 0, -5, 10 .
● Int id ;
● Here, id is a variable of type integer.
● Int id,age;

Floating types
● can hold real numbers such as: 2.34, -9.382,
5.0 etc.
● float price; // 4 bytes size
● double price; // 8 bytes size
● Both are floating types.

Character types
● Keyword char is used for declaring such
variables.
● char test = 'h';
● test is a character variable.
● The value of test is 'h'.
● No string type in C . alternative = char array
● Eg: char num[ ] = “hello”

I/O in C programming
● Two commonly used functions are printf() and
scanf().
● Function scanf() reads input.
● Function printf() prints output.

Format specifiers and ampersand
● scanf("%d”,&a); for int , &a means the address
of variable a
● scanf("%f”,&a); for float
● Scanf(“%c”,&ch);
● Scanf(“%s”,&word);
● printf("%d is value of a",a);

Operators
● to perform tasks including arithmetic, conditional and bitwise
operations
● Types :
1. Arithmetic Operators
2. Increment and Decrement Operators
3. Assignment Operators
4. Relational Operators
5. Logical Operators
6. Others (Conditional,Bitwise and Special Operators)

Increment and decrement operators
● Increment ++ increases the value by 1
● Decrement -- decreases the value by 1
● Example :
int a=5;
a++ . value of a is now 6
● Similarly, for a-- , a is 4

++ and -- operator as prefix and
postfix
● Postfix a++ → original value of a is returned
first then, a is incremented by 1.
● Prefix ++a → value of a is incremented by 1
then, it returns the value.

Decision Making
● If else
● Nested if else
● Loops

if and if else statement
1 . if (testExpression)
{
// statements
}
2 . if (testExpression) {
// codes inside the body of if
}
else {
// codes inside the body of else
}

Nested if...else statement
if (testExpression1)
{ // statements to be executed if testExpression1 is true
}
else if(testExpression2)
{ // to be executed if testExpression1 is false and testExpression2 is true
}
...
else
{ // statements to be executed if all test expressions are false
}

Loops
● are used to repeat a specific block of code.
● Types -
1 . for loop
2 . while loop
3 . do while loop

For loop
for (initializationStatement; testExpression;
updateStatement)
{
// codes
}

While loop
while (testExpression)
{
//codes
}

Do while loop
do
{
// codes
}
while (testExpression);

Break and continue statement
● Break→ terminates the loop
● Continue → skips some statement
● Syntax :
break;
continue;

Switch case
switch (n)
{
case constant1:
// code to be executed if n is equal to constant1;
break;
case constant2:
// code to be executed if n is equal to constant2;
break;
. . .
default:
// code to be executed if n doesn't match any constant
}

Functions
● a block of code that performs a specific task.
● Two types of functions :
1 . User defined functions
2 . Standard library functions

Standard library functions
● built-in functions
● handle tasks such as mathematical
computations, I/O processing, etc.
● Example : printf() and scanf()

Advantage of user defined functions
● Clean,easier to maintain.
● Reusability.
● Easy to debug.

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Programming basics

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