Introduction to C Programming

C Tokens

C Tokens are the basic building block of a C Program. There are 6 types of tokens in C Programming

Keywords

predefined words in a C Programming Language, which have special meaning in the language. Example: if, then, return, switch etc.

Identifiers

name given to a variable, functions or user defined data types in a C Program. They are case sensitive and can consist of letter, underscore and dollar signs.

Constants

These are the fixed values that cannot be changed during the execution of the program. C supports 4 constants: Integer, Floating point, character and String constants (sequence of characters enclosing).

Operators

These are the symbols used to perform arithmetic and logical operation in a C Program. Example: AND, OR, NOT, +, =, -, etc.

Punctuation Symbol

These are used to separate and group tokens in a C Program. Example: comma, semicolon, parenthesis etc.

Operators

Operators are used to perform operations on one or more operands. Operators supported by C Programming Language are

Arithmetic Operators

Used to perform arithmetic operations: Addition (+), Subtraction (-), Multiplication (*), Division (/) and Modulus (%).

Relational Operators

These operators returns a Boolean value, either true or false depending on whether the condition is satisfied or not. It includes less than (<), greater than (>), less than equals to (≤), greater than equals to (≥), equals to (==) and not equals to (≠).

Logical Operators

These are used to perform logical operations. It includes AND (&&), OR (||) and NOT (!).

Bit-wise Operators

It is used to perform bit level operations in a C Program. It includes bit-wise AND (&), bit-wise OR (|), bit-wise XOR(^), bit-wise NOT (~), left shift (<<) and right shift (>>).

Conditional Operators

The ternary operator is one of the conditional operators. The syntax is (condition) ? value1 : value2.

Size Operator

This operator returns the size of a variable or data type in bytes.

Comma Operator

The operator is used to separate multiple expression and execute them in order.

Formatted/Unformatted Input/output

Control Statements

Helps to specify a program control’s flow. Specify the order of execution of the instruction that are present in the program. It is used to make decisions, perform tasks repeatedly, jump from section of one code to another.

Decision Making

Also called IF-statements, and is executed when the evaluation of the condition is true. Examples: IF, IF ELSE, Nested IF etc.

Selection

Also called Switch Case. It can be used when more than three alternatives or conditions exist in a program. In every block there is a use of case keyword whereas break and default statements are optional.

Loops

It is a control flow statement that allows a program to repeat a set of statements while a certain condition is true. It includes For, While and Do While . It saves time, reduces error and make code more readable.

Jump Statement

It allows the flow to execution to jump from one part of the program to another.

1. **break statement:** terminates a loop or switch statement and transfer the control to the next statement outside the loop or switch.
2. **continue statement:** skip the current iteration of the loop and continue at the next iterations.
3. **break statement:** transfer control to another part of the program specified by a label.

Looping

For Loop

The initialization step will be executed only once, and then the condition will be checked, if the condition results in true, the loop will continue and if results in false, the loop with be terminated.

for(initialization, condition, increament/decreament) {
//code
}

While Loop

Perform only if the condition is valid, and will not be executed if the condition is incorrect.

while(condition) {
//code
}

Do While Loop

The condition will be evaluated at the end of each iteration. This loop will be executed at least once, even if the condition is set to false, as the condition is evaluated at the end of the execution.

do {
//code
} while (condition);

User-defined functions

Block of modular code that is written by the programmer which can be called in multiple parts of the program to make the code more modular, readable and maintainable. In simple words, its just a simple function that is created by the user.

return_type function_name(paremeter_list){
//function body
}

Recursive functions

Recursive functions are those functions that call itself during the execution of the program. It helps reduces the code size and makes the function reusable in a lot of cases. Exit condition is necessary, as it may leads to infinite call of the function.

Its often used to solve problem related to trees, linked lists, graphs. Tower of Hanoi is one of the problem that can be solved simply using the recursive function.

int factorial(int n) {
	if (n==0) {
		return 1; //Exit Condition
	} else {
		return n*factorial(n-1); //Recursive Call
	}
}

Arrays

Array is the collection of elements of same data type, stored in the contiguous memory location (lowest address corresponds to first element and the highest address to the last element). It is used to store multiple values in a single variable.

Advantages of arrays includes: sorting of data, ease of traversing etc.

data_type array_name[array_size];
 
int arr[10]; //int array of size 10 with name arr
 
int arr[5] = {1,2,3,4,5}; //array is declared with initialization

1-D Array

element stored in contiguous memory location.

2-D Array

It is an array of arrays where the inner array will represent a row in a 2D array. The elements are organized in rows and columns with each row being stored in a separate block of memory and can be accessed using two indices or subscripts.

int arr[5][6]; //declaration
 
int arr[3][2] = {{1,2,3},{4,5,6}}; //initialization

Multi-dimensional Array

In general, array of arrays are called multi-dimensional array. You can increase the dimension based on the requirements but the complexity increases as the dimension increases.

float arr[2][3][4]; //can hold 24 elements

String manipulations

It refers to manipulation of various operations that can be performed on strings (array of characters), such as concatenating, comparing, copying and formatting strings.

All functions are included by using string.h header and can be used to clean, preprocess and transform text data for analysis.

Mostly used string handling functions are: strcat(), strlen(), strcpy(), strcmp(),etc.