Adapted from
Differences Between C and C++
by Robert Niemann (Century College)
11/22/2015

Adapted by Mithat Konar

• You can't create classes or objects in C.
• You can't use any of C++'s predefined classes and objects.
  • cin
  • cout
  • string
  • class
  • etc.

• Input/output is generally more complicated in C.

• printf() write a formatted string to the display
• scanf() read a formatted string from the keyboard
• putchar() write a single character to the display
• getchar() read a single character from the keyboard
• puts() write strings to the display
• gets() read a string from the keyboard

• fopen() open a text file.
• fclose() close a text file.
• feof() detect end-of-file marker in a file.
• fscanf() read formatted string from a file.
• fprintf() write formatted string to a file.
• fgets() read a string from a file.
• fputs() write a string to a file.
• fgetc() read single character from a file.
• fputc() write a single character to a file.

• <stdio.h> input/output
• <stdlib.h> standard utility functions
• <string.h> string operations
• <ctype.h> character class tests
• <math.h> mathematical functions

• boolean type
• reference variables
• function overloading
• // single line comments in older versions of C.

• You must define variables at the beginning of a function.

int  main( )
{
    int a,b,c;
    float x,y,z;
    ...

• You don’t need function prototypes.
• Best practice to use them anyway.

int main()
{
    foo();
    return 0;
}
 
int foo()
{
    printf( "Hello world" );
}

• const is available only in newer versions of C.
• #define precompiler directive typically used instead of const.
• #define can also be used to create macros.

#define PI 3.1415
#define TAX_RATE 0.065
#define square(x) ((x) * (x))

• Different way to allocate/deallocate dynamic memory:

int *x = malloc(sizeof(int));            /* allocate a single int */
int *x_array = malloc(sizeof(int) * 10); /* allocate array of 10 ints */
 
/* release storage that was allocated */
free( x );
free( x_array );

• Need to use struct keyword when defining struct variables

struct MyStruct
{
    int x;
};
 
struct MyStruct aStructInstance;

• Look here.

• C Reference Card (ANSI)
• A C Tutorial from Tutorials Point