What is c programming
C is a procedural programming language. It was initially developed by Dennis Ritchie in the year 1972. It was mainly developed as a system programming language to write an operating system. The main features of the C language include low-level memory access, a simple set of keywords, and a clean style, these features make C language suitable for system programmings like an operating system or compiler development.
For C to be executable it must first be compiled
Introduction to gcc
The original author of the GNU C Compiler (GCC) is Richard Stallman,the founder of the GNU Project.
gcc stands for GNU compiler collections which is used to compile mainly c and c++
To check gcc version present in you system use the following command
gcc -v
syntax
gcc [-C | -S | -E |] [-std = standard]
Compilation
Compilation refers to the process of converting a program from the textual source code, in a programming language such as C or C++, into machine code, the sequence of 1’s and 0’s used to control the central processing unit (CPU) of the computer. This machine code is then stored in a file known as an executable file, sometimes referred to as a binary
file.
A compiler is a computer program that translates the source code written in a high-level programming language(i.e C) to a low-level language such as machine code.
The compilation process
There are four main steps involved in the compilation process as mentioned below:
- Preprocessing
- Compiling
- Assembling
- Linking
Preprocessing
This is the first phase through which the source code is passed.
- This phase includes:
- Removal of comments
- Expansion of included files
- Conditional combination
- inclusion of the code from the header files
Its output is stored with a file extesion of
.i
To view the output of the pre-processing stage, we can use the command gcc -E filename.c option as shown below.
root@DESKTOP-TI71NAL:~# gcc -E helloworld.c
Compiler
In this phase compilation of the filename.i happens in order to compile an output file of filename which is in an assembly level
username@hostname:~$ gcc -S filename.c
Assembler
Here is where filename.s is taken as input and turned into filename.o by the assembler.
gcc -c filename.c
Linker
This the final phase in which all the linking of function call with their definitions are done.
gcc by default does dynamic linking and so printf() is dynamically linked.
The tasks performed by the linker include:
- Linking together all the object files from the different source files.
- Linking function calls with their definitions. The linker knows the locations of the function definitions in the static or dynamic libraries. Option 1
Run the following command:
username@hostname:~$ gcc helloworld.c
When you run this command, the compiler generates an executable program called a.out. To run the executable program type the following command:
username@hostname:~$ ./a.out
Option 2
To give the executable program a different name, we can add the "-o" option to the gcc command after the name of the file we are compiling, as shown below:
username@hostname:~$ gcc helloworld.c -o helloworld
To run the executable program, use the command below:
username@hostname:~$ ./helloworld
## gcc options
-o this option is used for output
this will compile the filename.c , but instead of giving the default name it is executed using ./filename
gcc filename.c -o filename
-werror This compiles the source and show the warning if any error is present in the program.
gcc filename.c -werror -o filename
-wall this not only checks the errors but any other kind of warning
gcc filename.c -wall -o filename
Thanks for reading
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