How to write a C program? Basic rules for writing C programs

A C program is a set of statements written in the C programming language. Every program should follow some standards (rules) to make our code easy to view and maintain. The following article will introduce you to some basic writing rules of C programs. I hope it will be helpful to you. [Recommended related video tutorials: C Language Tutorial]

## Comments

Comments are not required, but they are just as important as the code. So the first rule is to remember how to comment (document) your code correctly.

Why comments? What are comments used for?

1. Explain the purpose of the code.

2. Explain each logic or algorithm, what is it and why is it used?

3. Each function declaration and definition should be documented and have comments to introduce usage and functions.

4. Comments allow others to understand other people’s code faster and easier, making it easier to use and maintain the code.

After the statement ends, it needs to be terminated with a semicolon (;)

Statements that need to be terminated with a (;)

● All printf(), scanf() or any other function calls.

● All declarations, such as variables, constants, functions, and structures must end with a semicolon.

● All expressions must end with a semicolon (;).

Example:

int a; //变量声明
printf("Hello!"); //一输出声明
sum = findSum (10,20,30); //函数的调用语句
.......

Statements that do not need to be terminated with (;)

● Header file include statement.

● Macro definition statement.

● If statement, loop statement, function header and function definition.

#include <stdio.h> //头文件
#define MAX_LEN 1024 //宏定义语句
int main()      //主函数定义部分
{
语句.......
}
//函数头，其定义为
int findSum(int a, int b, int c) 
{
return (a+b+c);
}
if(a > b) //if 语句
large =a;
else
large =b;
........

Related rules for tokens and identifiers

We need to understand keywords and know some rules for identifiers.

Some points you must know:

● Keywords are reserved words in the compiler and cannot be used for other purposes.

● C language is a case-sensitive programming language. Here, lowercase identifiers and uppercase identifiers are different. Therefore, if you declare a variable named Num, you must use Num everywhere; you cannot use num, NUM, etc. instead of Num.

● Like keywords, library functions are also declared in header files, and header files must be included in the program. For example, if you use the sqrt() function to find the square root of any number, you must include the math.h header file.

Rules about identifiers (variable declarations)

● It is allowed to use lowercase, uppercase letters, numbers and underscores (_) to define identifiers symbols (i.e. variable names, constant names, function names, etc.).

● Only letters or underscores (_) can be used as the first letter at the beginning of the identifier.

● Spaces and other special characters are not allowed in identifier names. If there are two words in the identifier name, you can use underscores (_) to separate them, or use camel case to write the identifier name. .

For example: If you want to declare a variable to store the roll number, the variable name should be roll_number or rollNumber or anything like that, but no spaces.

● Identifiers must be meaningful and descriptive.

● You cannot use keywords as identifier names

Code indentation

Code indentation is when writing a program Very important; indented code makes it easier to read and edit. Example:

Indented code

#include <stdio.h>
int main()
{
	int a;
	int b;
	int c;
	a = 10;
	b = 20;
	if(a>b)
	{
	   c=a;
	   a=b;
	   b=c;
	   printf("从小到大输出： %d,%d\n",a,b);
	}
	else{
		printf("从小到大输出： %d,%d\n",a,b);
	}
	return 0;
}

Unindented code

#include <stdio.h>
int main(){
int a;int b;int c;
a = 10;b = 20;
if(a>b){c=a;a=b;b=c;printf("从小到大输出： %d,%d\n",a,b);}
else{printf("从小到大输出： %d,%d\n",a,b);}
return 0;}

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