• Table Of Content

Overview

General purpose programming language

In the past, languages were used for specific purposes, such as FORTRAN for calculations, COBOL for business-oriented applications.

C is a general usage imperative programming language.

The History of C

• It all started with a research paper on a new programming language C by Dennis Ritchie and Ken Thompson
• C was derived from language B (Ken Thompson) which originated from BCPL (Basic Combined Programming Language @Martin Richards)
• By 1970, C evolved into now 'Traditional C'
• Due to the rapid expansion of C, many hardware-depend variants came into the picture, which were similar to Traditional C but incompatible, so a committee was formed for its standardisation, ANSI (American Standard Standards Institute)

What does it provides?

• Very fast (almost similar to assembly)
• Cross-platform code (mostly)
• Highly flexible viz. has a lot of libraries
• Takes advantage of capabilities of the current compilers
• Provides low level access to memory and lets us efficiently manipulate it, but there is a trade-off b/w freedom and responsibility and it allows C to be used for both system programming and application programming.
• Portability: Cross-platform support for the C-code due to the availability of powerful compilers

>The Standard C

• Standards version of C were created then (C/89, C99 and C11)
• Programs written in C written w/o any hardware-dependent assumptions will run correctly on any platform if compiled by a Standard C compiler

<aside> 👉 C89

</aside>

• aka ANSI C
• Supported by current C compilers
• It's the base of all the revised standards

<aside> 👉 C99

</aside>

• Revised standard of C89 that expands its capabilities such as variable length arrays, single line comments etc, true/ false of stdbool.h
• Not widely adopted and not a lot of compilers support it

<aside> 👉 C11

</aside>

• The current standard
• Support by current C compilers

>Working With Larger Programs

• Before even starting to write code, we should decide how to break down the program into multiple modules. Writing the entire code in a single file and then later debugging and trying to break it down will leak to failure and rewriting the code from scratch.
• We should break down a large codebase into smaller modules, and all type of similar code should be in a module.
• We should use an IDE when dealing with a large codebase.
• We should leverage these techniques of typedef and #define, to do just like MS did with Hardware Abstraction Layer, and write very machine independent code. When a machine requires long, instead of using machine dependent code, we replace it with generics and we'd just typedef long hello, instead of typedef int hello, and our code will be free from any architecture-specific dependency. Same with #define

Fundamentals Of C

>Mind Map of the Basics

>Basic Structure of a C program

#include <stdio.h> //preprocessor directives
#include <otherLibrairies>

int main()  //main function initialisation, everything inside will be executed. Must be used only once
{
	printf("My name is Rohit");  //statements  // { } are terminal points of a function, and inside them is blocks of code
	return 0;
}

>Comments

- Used to document our code
- Extraneous comments are bad, avoid them.

Single Line Comment
//This is a single line comment

Multi-line comment
/* This is a 
multi
line 
comment
*/

>Escape Characters

• Special characters which represent certain actions such as backspacing, going to the next line etc
• They must be enclosed within single quotes when assigned to a character variable, because a char data-type only accepts single quote

char x = '\\n'; 

Preprocessors and Headers

>Pre-Processing

• These special statements are identifier by the presence of the character #, and it must be the first non-spaced character in the line
• By using #something (pre-processor directive), we're giving an instruction to our compiler to do something with it before the compilation of the source code takes place
• Since they're dealt with, at the pre-processing phase, they don't have any global, local scope
• These pre-processor directives are restricted to just one line in length

>Header Files

• It defines information about some of the functions that are provided by that file
• They end with .h extensions
• Case-sensitive on some systems
• Normally, no executable code is there in the header files, no logic, only definitions of functions.

>The include preprocessor directive

A pre-processor directive, which instructs the compiler (#include <header.h>) to include the contents of the header library in our program.

/* < > tells the compiler to look for this 
file in directories defined by $PATH*/
#include <stdio.h>

/*Used to include user-defined libraries, 
Tells the compiler to look for a header file in the current directory*/
#include "stdio.h"

The basic Important Stuff