No More Black Boxes: Understand How Systems Work with C

Through C language, we can explore the working principle of the system, including: C language basics: data types, variables, operators, control flow, memory management Memory management: pointers, memory allocation and release functions System calls: interacting with the operating system , such as file operations, process management, external command execution practical cases: the working principle of file I/O, such as opening files, reading content, printing content, closing files

No more black boxes: Use C to understand how the system works

Introduction

Understanding how the underlying system works is essential for developing efficient and reliable software It's important. The C language is ideal for exploring system complexity because of its proximity to the hardware and the direct control it provides over system behavior.

C language basics

First, let us review the basic concepts of C language:

• Data types
• Variables
• Operators
• Control Flow

Memory Management

Memory management in C is important for understanding how the system stores and crucial for handling data:

• Pointers: allow direct access to memory locations
• Memory allocation and deallocation functions: malloc() and free()

System calls

C language interacts with the operating system through system calls:

• open(), read(), write(): file operations
• fork(), exec(): Process management
• system(): Execute external commands

Practical case: Understanding file I/O

We will build a simple program to illustrate how file I/O works:

#include <stdio.h>

int main() {
  FILE *fp = fopen("test.txt", "r");
  if (fp == NULL) {
    perror("Error opening file");
    return 1;
  }

  char buffer[1024];
  while (fgets(buffer, 1024, fp) != NULL) {
    printf("%s", buffer);
  }

  fclose(fp);
  return 0;
}

In this program:

• fopen() Function Open a file named "test.txt" for reading. The
• fgets() function reads the file content and stores it in the buffer array. The
• printf() function prints the content read on standard output.
• fclose() function closes the file.

Conclusion

By using the C language and system calls, we can gain insight into how the system works and gain control over the underlying operations. This is crucial for developing efficient, portable, and reliable software.

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