The basic in C programming With full detail description

basic in c programming

in the first place, C is a general-purpose programming language, which was designed by Dennis Ritchie in 1972 and C is not a very high-level language

in reality, It will be little difficult to understand C if we compare with a high-level language like python

on this occasion, suppose, if you are planning to learn C++, C#, and Java it is better to learn C first

But, why?

because C++, C#, and Java are based on C.

Why C is called a system programming language?

Because it is used for writing compilers and operating systems

In other words, C language is used for writing operating systems due to its closeness to the hardware

in brief, C is a small language

But, why do you say it is a small language?

Because C offers only single thread control flow tests, subprograms(recursion,function), loops, statement grouping

on the other hand, C does not support multiprogramming, parallel operations, coroutines, and synchronization

There are only 32 keywords available in C but when we compare them to C++ keywords, every new standard[C++11, C++14, C++17,  C++20] has new keywords

on the whole, C is not a strongly-typed language

But, why do you say C is a weekly typed language?

To illustrate that C is a weekly typed language I will use two concepts

1. Data type conversion
2. Function prototypes

Data type conversion

For example: In weekly typed programming language if we subtract an integer with string at that instant, the code will get executed but with some warning even though it is a data type mismatch

But the same thing is not possible in strongly typed programming languages like C++ where the compiler will through an error

But,why?

Because of the  data type mismatch

The strongly typed language will throw an error: explicit (outside) conversion is required while on the other hand, the weekly-typed language will compile the code by implicit (inside) that is, data type conversion done by the compiler

to demonstrate, a C example that is, for the subtraction of an integer with a string

#include <stdio.h>
int sub_two(int x, int y){ //Function
    return x - y;
}
int main(){
    int a=12, sub;//integer
    char b[]="sub";//string 
    sub = sub_two(a, b); //function call
    // Displaying output
    printf("subtraction of two items: %d", sub);

    return 0;
}

Output

subtraction of two items:-2686712

this time, a C++ example for the subtraction of an integer with a string

#include <iostream>
using namespace std;

int sub_two(int x, int y){ //Function
    return x - y;
}

int main()
{
    int a=12, sub;//integer
    char b[]="sub";//string 
    //function call
    sub = sub_two(a, b); // error: invalid conversion from char* to 'int'
    // Displaying output
    cout << "subtraction of two items:" <<sub<<endl;
    return 0;
}

Function prototypes

as a matter of fact, in C you can call the function pow() without including the header file #include<math.h>

but with little warning

Whereas in C++ you can not call a function pow() without including the header file #include<math.h>

But, why?

Because C++ has strong type checking that doesn’t allow any function call without its function prototype #included

#include <stdio.h>
//#include <math.h>

int main()
{
    int a=2,b=3,c;
    c=pow(a,b);//warning implicit declaration of function 'pow'
    printf("power=%d",c);
    return 0;
}

Output

power=8

at this time, a C++ example to show that if we did not include a file called #include<math.h> in the program then, in that case, if we called the function pow() will result in an error

#include <iostream>
//#include <math.h>
using namespace std;

int main()
{
    int a=2,b=3;//error 'pow' was not declared in this scope if you did not file #include<math.h>
    cout << "power=" <<pow(a,b)<< endl;
    return 0;
}

The drawback of C language

in essence, the major problem with C language is its concept called pointer

on one hand, Pointer errors are difficult to find, and pointers are not secure from the security and safety point of view    

on the other hand, Pointers are the main culprits for memory leakage in the program

in truth, Java is created to avoid the notorious pointers  bugs of C/C++

Difference between low-level language C and high-level language Python

#include <stdio.h>
int main()
{
    printf("Hello world!\n");
    return 0;
}

print('Hello, world!')

at this point, well, imagine this

 for instance, suppose, you like to print hello world! With low-level language C and high-level language Python

Next, when you wrote a C program to print hello world! you need 6 lines of instruction and while, on the other hand, you just need one line of instruction to print hello world! With Python

in this situation, can you deconstruct the difference between the low-level language C and the high-level language Python?

in fact, Python is pretty effective, right?

But, why?

Because you need just one line of instruction in python to express yourself  to complete the task

On the other hand, in C you need 6 lines of instructions to express yourself  to complete the required task

So, what’s the conclusion?

High-level languages like Python are effortlessly easy to write and read as well as shorter

If that is true, then why do we need C which is a nightmare to read and write as well as long

Because C is a compiled language that means C will execute the instructions faster when compared with Python

so far, clear as mud?

Difference between C and C++

#include <stdio.h>
int main()
{
    printf("Hello world!\n");
    return 0;
}

#include <iostream>
using namespace std;
int main()
{
    cout << "Hello world!" << endl;
    return 0;
}

Here’s another one

at this instant, suppose, you like to print hello world! With C and C++

until now, okay,

in short, Yes! We wrote hello world! Programm in C and C++

with this in mind, next, what?

to sum up, can you spot the difference between C and C++ hello world! program

of course, No!

But, Why?

Because they look quite similar to each other right?

Yes! Because both C and C++ are low-level languages and any valid C program is also a C++ program

Then what is the difference?

C++ means it is an extension of C  with some added features such as OOPS

Writing a program in C

1. Define the program objectives
2. Design the program
3. Write code
4. Compile
5. Run the program
6. Test and debug
7. Maintain the program

Standard header files

Structure of a C program

Main( )
{
            Statement 1;
             .......
             .....n;
}
Function 1( )
{
            Statement 1;
             .........
             .......n;
}
Function 2( )
{
              Statement1;
              .......
               ....n;
}
Function N( )
{
              Statement 1;
              ..........
               .......n;
}

Writing a simple C program

on one hand, Return 0 means the integer value return by main() function indicates success in compiling the given code

on the other hand, Return a non zero if the main() function fail to do its intended work. next, that indicates failure in compiling the given code

Statement terminator

that is to say, every statement you write with  c program must be terminated with a semicolon(;)

Input and output function

not to mention, scanf () function receives input values and printf() function print output values on the screen

Syntax of a printf() function

Printf("<format string>",<no of  variables>);

<format string> contain

Int uses %d
Float uses %f
Char uses %c
Character string uses %s

Example

Printf("%d", x);
scanf("%f%f%d",&x,&y,&z);

We use scanf() to receive input values from user

Example

Scanf("%d",&x);
printf("%f%f%d", x,y,z);

Note: the difference between printf() and scanf() function

use address operator(&) in front of variable for scanf() function

What is a  main()  in c program?

It is a function, which you can consider as a vessel with a set of statements in it.

Int main()
{
Statement1;
...................
..................n;
}

The datatype int kept in front of main() function to return an integer number

How to comment in a c program?

Comments in a c program must be enclosed within asterisk(*)

/* this is a comment*/

resources

• Let us C by Yashavant Kanetkar
• Let us C++ by Yashavant Kanetkar
• The C programming language by Brian w.Kernighan Dennis M.Ritchie
• Python programming an introduction to computer science by John Zelle