Speak the Language of Systems: Learn C, One Line at a Time

By analyzing the C code line by line, we can master the basic concepts of the system language: include header files contain functions. The int main() function is the program entry point and returns an integer. The printf() function prints information to the console. return 0 ends the program and returns 0 to the operating system. Variable declaration allows data to be stored. The printf() and scanf() functions take user input. Calculations can perform mathematical operations to determine results. The printf() function displays the results.

Learn system language with line of C code

C language is the cornerstone of learning system language, it is both powerful and elegant. By breaking down C code into line-by-line parsing, we can gain insights into the basic concepts of computer systems.

Learn line by line

To learn C, we start with a line of code:

#include <stdio.h>

int main() {
  printf("Hello world!\n");
  return 0;
}

Parsing a line of code

Every line reveals the power of C language.

• #include <stdio.h>: Standard header file containing input/output functions.
• int main(): The entry point of the program, returning integer type.
• printf("Hello world!n"): Print "Hello world!" to the console.
• return 0: End the program and return 0 to the operating system.

Practice: Write a program to calculate the area

Now, write a program to calculate the area of ​​a rectangle in C code:

#include <stdio.h>

int main() {
  int length, width, area;

  printf("Enter the length of the rectangle: ");
  scanf("%d", &length);

  printf("Enter the width of the rectangle: ");
  scanf("%d", &width);

  area = length * width;

  printf("The area of the rectangle is: %d\n", area);
  return 0;
}

Parse line by line

• int length, width, area;: Declare variables for storing length, width and area.
• printf and scanf: used to get input from the user.
• area = length * width;: Calculate the area.
• printf: Print the result.

Summary

By learning C code line by line, we can gradually master the language of the system. From basic I/O functions to complex data structures, the C language provides powerful tools for interacting with computer systems.

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