Learn C Language with Free Lessons & Tips

Language is a medium for communication. If we want to perform anything with another person, we can know the human language as a human being. Similarly, if we want to perform anything with a computer, we need to know some computer language.

Computer languages are at three levels:

 

• Machine level (or) Low-level language: These languages consists only of zeros and ones (binary language). The system can directly understand this language. Processing of instructions is very fast and effective. At the machine level, each and every instruction is a sequence of zeros and ones only. But, it is very difficult to remember all instructions as a sequence of 0’s and 1’s.

 

Ex: If we want to add 10 and 12, we need instruction as below.

 

11010101 00001010 00001100

 

In the above example, the code 11010101=> ADD, 00001010 =>10, 00001100 =>12.

 

• Assembly level language: These languages consist of Mnemonics means English shortcut codes like ADD, SUB, MUL… It is better to remember for programmers. But, these instructions are not directly understood by the computer.

So, here we need a translator for converting assembly level instructions to machine language instructions. The translator which converts assembly language to machine level language is known as ASSEMBLER.

• High-level language: These languages are seemed to be English like languages. These languages are easy to implement for programmers. But, these instructions are not directly understood by the

 

So, here we need a translator which converts high-level language instructions to machine level language instructions. The translator which converts high-level language instructions to machine level language instructions is known as COMPILER (or) INTERPRETER.

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The object file is in binary code, and the machine understands the binary language. So why object files are not executed? read less

Void main () is the entry point for execution in C program. The void is a keyword that represents function will not return anything but a void value.

Main is the name of the function and () represents parameter list that can be passed to function in this case nothing is passed.

Syntax of main function is :
dataType main()
{
// your code here

}

in the above function, dataType is the type of data (int, float or string) return by the main function.

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C programming language was developed in 1972 by Dennis Ritchie at AT&T Bell Labs.

It was developed to overcome the problems of languages such as B, BPCL.

It was developed to write the Unix operating system. The Unix OS was written entirely in C.

The language was formalized in 1988 by ANSI.

C is the most widely used and popular system programming language.

Microsoft's Windows kernel is mostly written in C language.

Linux OS is also written in C language, with some parts in Assembly.

Mac computers are also powered by C.

The world's most popular databases, including Oracle, MySQL, PostgreSQL, SQL Server are coded in C and C++.

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C is an procedure oriented programming language. For any begginer the word program is new.

 

Program: Set of instructions to be followed by machine or computer.

 

Instruction Examples: Arithmetic instruction like 

a=b+c;

 Semi colon here indicates end of instruction.

Collecting different variety of instructions into one name and executing it on machine. That one common name is noting but a procedure, function or method.

A C program can have n number of methods.

First sample program:

#include 
int main()
{
   // printf() displays the string inside quotation
   printf("Hello, World!");//printf is a predefined library function
   return 0;
}

First Line of program includes the header file . #include  is a preprocessor command. This command tells compiler to include the contents of stdio.h (standard input and output) file in the program.
Header files in C contaions predefined function definitions. Example: printf(); 

main(): Function that starts the execution of program.

int: here it is return type of main()
A function can return any type of value.Here main is returning int so last line of program 
contains return statment having default int value 0. 

 After compiling  this program we get the filename.obj file. Linker performs linking and at the end we get filename.exe. This exe file is an executable file which is finally executed.

 

 

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Lower order and higher-order bytes are the terms used while computing calculations in a programming language. Usually, numbers are written from left to right. The left is the most significant bit, and it is written first. 

 

For example, if we consider your paycheck, then you would be happier if the number the first digit increases instead of the last digit. This is what is referred to as "significance" of a digit. 

The bits present in computer memory are written usually with a base 2 (for binary, the base is considered as 2). So, the least significant bit is represented as one. The next bit is represented as two or 2'1 and the next one as 2'2'1 and so on..

 

For example, if we consider 2 bytes of memory, which represents a 16-bit number, then one byte will hold at least eight significant bits, and the other byte will hold the most significant 8 bits. 

The byte that contains the most significant 8 bits is called the higher-order byte and the one that contains the least significant bits is called the higher-order byte. 

 

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getch() is used to hold the console(output) window on the screen after the whole program run is completed till the user enters a key from keyboard. However, the character entered is not displayed on screen. For that you will have to use getche() function. Both functions are present in conio.h header file.... read less

The header file which is added to the program that one has written is basically what 'include stdio.h.' means. Stdio.h is known to contain the input and output operations like "printf" or "scanf" etc. "h" extension means the header file.

If you request to use a header file in the program by actually including it with the preprocessed C directive #include like you have seen the inclusion of stdio.h header file, which comes along with the compiler you are using.

If the header file is equal to that of copying the header file, it is advised not to do it because it would be inevitable to get an error and it's, of course, a bad idea to copy the content of the header file into its designated source files, as in if at all one has multiple source files in a written program.

In layman's terms, It's effortless .#include is what is known as a "preprocessor". As the name suggests, it is preprocessed before the code. These preprocessor statements are compiled before any other code in your script.
Hope this helps

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