Basics of C programming language

  • Every C program has a main(). This is the starting point of execution after a program is loaded into memory
  • Every statement must end with a ;
  • Comments start with //

Data Types in C

  • Data types determine how much memory/space is offered to the data
  • Also, how the data is displayed
  • Declaration statements must have data type before the variable name e.g. int score
  • Space in memory is reserved at the time of execution

    • int - 4 bytes (32 bits)
    • short -
    • long -
    • float real number
    • double big real number
    • char - used to store a single character

C vs C++

#include <stdio.h>

int main() {
  printf("bonjour le monde!");
  return 0;
#include <iostream>
using namespace std;

int main() {
  printf("bonjour le monde!");
  return 0;
  • iostream is a C++ library for input-output. The C equivalent would be stdio.h
  • use gcc and g++ to run you C and C++ code respectively

Header files

  • Allow you to use functionality from other files and modules

Logical operators

  • The && operator has a higher precedence than the || operator.
  • The ! sign is used for logical negation

Overflow conditions

Overflow condition occurs when you are trying to save a value that can not be stored in the amount of memory it has been allocated. When such a condition occurs, it’ll end up in:

  • Run time error (undetected by the compiler)
  • Extra bits will be wasted and only the amount that can be stored will be saved, discarding rest

Flow diagram

  • Diamond = decision
  • Rectangle = process
  • Line = flow

while vs. do-while

  • while is executed zero or more times, meaning it may not even execute a single time if the condition is false.
  • do-while is executed one or more times, meaning it runs at least once.

For example, in guessing games, you know you’re going to make at least one guess, and if the first one isn’t right then continue making guesses..

  • Basically, in while the condition is tested before the loop and in do-while the condition is tested after the loop

for loop

for ( initialization condition ; continuation condition ; incrementing condition )


Top-down designing mechanism is based on the principle of ‘divide and conquer’ i.e. we divide a big task into smaller tasks and then accomplish them.

Functions are of two types

  • Funcs that return values (must return a valid data type, only one data type can be used)
  • Funcs that don’t return values (data type is void, may only display data to screen)
return-value-type function-name( argument-list )
  declarations and statements
  • If no data type is specified for return, default is int
  • Arguments passed to the function need to be a valid data type as well