Core Syntax of C Language

The C language, as a widely used and highly influential programming language, has its core syntax that constitutes the foundation of program design. Mastering these core syntax elements is key to in-depth learning of C language, enabling the development of various efficient and stable programs.

Variables and Data Types

In C language, a variable is the basic unit for storing data. A variable must be declared before it can be used. When declaring a variable, its data type must be specified. Common data types include integer (int), floating-point (float, double), and character (char).

#include <stdio.h>
int main() {
    int num = 10;
    float f = 3.14f;
    char ch = 'A';
    printf("The value of integer variable num is: %d\n", num);
    printf("The value of floating-point variable f is: %f\n", f);
    printf("The value of character variable ch is: %c\n", ch);
    return 0;
}

In the above code, integer variable num, floating-point variable f, and character variable ch are declared and initialized, and then the printf function is used to output the values of these variables to the console.

Operators

The C language provides a rich set of operators, including arithmetic operators (+, -, *, /, %), assignment operators (=), comparison operators (==, !=, >, <, >=, <=), and logical operators (&&, ||, !).

#include <stdio.h>
int main() {
    int a = 5, b = 3;
    int sum = a + b;
    int diff = a - b;
    int product = a * b;
    int quotient = a / b;
    int remainder = a % b;
    printf("The result of a + b is: %d\n", sum);
    printf("The result of a - b is: %d\n", diff);
    printf("The result of a * b is: %d\n", product);
    printf("The result of a / b is: %d\n", quotient);
    printf("The result of a %% b is: %d\n", remainder);
    return 0;
}

This code demonstrates the use of arithmetic operators, performing addition, subtraction, multiplication, division, and modulus operations on two integer variables and outputting the results.

Control Structures

1. Sequential Structure: The program executes statements in the order they appear, which is the most basic structure.
2. Selection Structure: Implemented through if-else statements and switch statements.

#include <stdio.h>
int main() {
    int num = 10;
    if (num > 0) {
        printf("num is a positive number\n");
    } else if (num < 0) {
        printf("num is a negative number\n");
    } else {
        printf("num is zero\n");
    }
    return 0;
}

The above if-else statement determines the positivity or negativity of num based on its value.

#include <stdio.h>
int main() {
    int day = 3;
    switch (day) {
    case 1:
        printf("Monday\n");
        break;
    case 2:
        printf("Tuesday\n");
        break;
    case 3:
        printf("Wednesday\n");
        break;
    default:
        printf("Other\n");
    }
    return 0;
}

This switch statement outputs the corresponding weekday information based on the value of day.

Loop Structures: Mainly includes for loops, while loops, and do-while loops.

#include <stdio.h>
int main() {
    int i;
    for (i = 1; i <= 5; i++) {
        printf("%d ", i);
    }
    return 0;
}

This for loop code iterates from 1 to 5, outputting the value of i in each iteration.

#include <stdio.h>
int main() {
    int i = 1;
    while (i <= 5) {
        printf("%d ", i);
        i++;
    }
    return 0;
}

The while loop repeatedly executes the loop body while the condition is satisfied.

#include <stdio.h>
int main() {
    int i = 1;
    do {
        printf("%d ", i);
        i++;
    } while (i <= 5);
    return 0;
}

The do-while loop executes the loop body once before checking if the condition is satisfied.

Functions

A function is an important tool for implementing modular programming in C language. It encapsulates a relatively independent block of functional code for easy reuse.

#include <stdio.h>
int add(int a, int b) {
    return a + b;
}
int main() {
    int result = add(3, 5);
    printf("The result of 3 + 5 is: %d\n", result);
    return 0;
}

The above code defines an add function that calculates the sum of two integers, calling this function in the main function and outputting the result.

The core syntax of C language is far more than this, but mastering the basics such as variables and data types, operators, control structures, and functions is like obtaining the key to unlock the door to the world of C programming. Through continuous practice and learning, one can gradually gain a deeper understanding of the powerful features of C language and write more complex and efficient programs.