C language is a high-level programming language widely used in system development and embedded programming. Its basic units include data types, variables, constants, operators and expressions. When writing C language programs, an in-depth understanding of these basic units is crucial to understanding the execution process of the program, optimizing the code structure, and improving programming efficiency. This article will lead readers to have an in-depth understanding of the basic units of C language through specific code examples.

1. Data types

The data types in C language can be divided into two types: basic data types and derived data types. Basic data types include integers, floating point types, character types, etc., while derived data types include arrays, structures, pointers, etc. The following code examples demonstrate the definition and use of data types in C language:

1. Integer data type:

#include <stdio.h>

int main() {
    int num = 10;
    printf("Integer data: %d
", num);
    return 0;
}

2. Floating point data type:

#include <stdio.h>

int main() {
    float num = 3.14;
    printf("Floating point data: %f
", num);
    return 0;
}

3. Character data type:

#include <stdio.h>

int main() {
    char ch = 'A';
    printf("Character data: %c
", ch);
    return 0;
}

2. Variables

In C language, variables are used to store data, and their data types need to be defined in advance. Here is a code example for the variable:

#include <stdio.h>

int main() {
    int a, b;
    a = 10;
    b = 20;
    int sum = a b;
    printf("Result of adding two variables: %d
", sum);
    return 0;
}

3. Constants

Constants are fixed data in the program. Constants can be literal constants, symbolic constants or enumeration constants. The following is a code example for constants:

#include <stdio.h>

#definePI 3.14159

int main() {
    const int num = 5;
    printf("Value of constant PI: %f
", PI);
    printf("Value of constant num: %d
", num);
    return 0;
}

4. Operators and expressions

In C language, operators and expressions are used to perform various mathematical operations and logical operations. Here are code examples for some common operators and expressions:

1. Arithmetic operators:

#include <stdio.h>

int main() {
    int a = 10, b = 5;
    printf("a b = %d
", a b);
    printf("a - b = %d
", a - b);
    printf("a * b = %d
", a * b);
    printf("a / b = %d
", a / b);
    printf("a %% b = %d
", a % b);
    return 0;
}

2. Logical operators:

#include <stdio.h>

int main() {
    int a = 5, b = 10;
    if (a > b && b != 0) {
        printf("a is greater than b and b is not 0
");
    } else {
        printf("Condition is not true
");
    }
    return 0;
}

Through the above code examples, readers can have a deeper understanding of the basic units of C language, including data types, variables, constants, operators, expressions, etc. Through continuous practice and practice, readers will be able to master the basic knowledge of C language proficiently and lay a solid foundation for further in-depth study.

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