Cprogramming 简明教程

int main() {
   return 0;
}

// This is a single-line comment

/*
This is line 1
This is line 2
..
*/

printf("Hello world");

scanf("format_specifier", &variable_name);

#include <stdio.h>

int main(){

   int age = 18;

   float percent = 67.75;

   printf("Age: %d \nPercent: %f", age, percent);

   return 0;
}

Age: 18
Percent: 67.750000

printf("Hello world");

scanf("%d", &x); // Integer input
scanf("%f", &y); // float input
scanf("%c", &z); // Character Input
scanf("%s", name); // String input

#include <stdio.h>

int main() {
   int num;

   printf("Input any integer number: ");
   scanf("%d", &num);

   printf("The input is: %d\n", num);

   return 0;
}

Input any integer number: The input is: 0

age, _name, person1, roll_no

data_type variable_name;

result = num1 + num2;
if(result >=10){
   printf("Greater than 10.");
}

if(boolean_expression) {
   /* statement(s) will execute if the boolean expression is true */
}

if (Boolean expr){
   Expression;
   . . .
}
else{
   Expression;
   . . .
}

if(condition1){
}
else if(condition2){
}
…
else{
}

if (expr1){
   if (expr2){
      block to be executed when
      expr1 and expr2 are true
   }
   else{
      block to be executed when
      expr1 is true but expr2 is false
   }
}

switch (Expression){

   // if expr equals Value1
   case Value1:
      Statement1;
      Statement2;
      break;

   // if expr equals Value2
   case Value2:
      Statement1;
      Statement2;
      break;
      .
      .
   // if expr is other than the specific values above
   default:
      Statement1;
      Statement2;
}

(condition) ? true_block: false_block;

while(test_condition){
   // Statement(s);
}

do{
   // Statement(s);
}while(test_condition);

for(initialization ; test condition ; increment){
   // Statement (s);
}

//Statement(s)
if(test_condition){
   goto label_name;
}

while(condition1){
   . . .
   . . .
   if(condition2)
   break;
      . . .
      . . .
}

while (expr){
   . . .
   . . .
   if (condition)
      continue;
   . . .
}

#include <stdio.h>

// Function declaration
int add(int, int);

// Function definition
int add(int a, int b) { return (a + b); }

int main() {
   int num1 = 10, num2 = 10;
   int res_add;

   // Calling the function
   res_add = add(num1, num2);

   // Printing the results
   printf("Addition is : %d\n", res_add);

   return 0;
}

Addition is : 20

type array_name [size1];   // One-dimensional array
type array_name [size1][size2];   // Two-dimensional arrays
type array_name [size1][size2][size3];    // Three-dimensional arrays

#include <stdio.h>

int main(){
   int numbers[5] = {10, 20, 30, 40, 50};

   int i;  // loop counter

   // Printing array elements
   printf("The array elements are : ");
   for (i = 0; i < 5; i++) {
      printf("%d ", numbers[i]);
   }

   return 0;
}

The array elements are : 10 20 30 40 50

#include <stdio.h>

int main () {

   /* an array with 5 rows and 2 columns*/
   int a[5][2] = { {0,0}, {1,2}, {2,4}, {3,6},{4,8}};
   int i, j;

   /* output each array element's value */
   for ( i = 0; i < 5; i++ ) {
      for ( j = 0; j < 2; j++ ) {
         printf("a[%d][%d] = %d\n", i,j, a[i][j] );
      }
   }

   return 0;
}

a[0][0] = 0
a[0][1] = 0
a[1][0] = 1
a[1][1] = 2
a[2][0] = 2
a[2][1] = 4
a[3][0] = 3
a[3][1] = 6
a[4][0] = 4
a[4][1] = 8

char string_name[size];

scanf("%s", string_name);

printf("%s", string_name);

#include <stdio.h>

int main() {
   char name[20];

   printf("Enter a name: ");
   scanf("%s", name);

   printf("You entered: %s", name);

   return 0;
}

struct struct_name {
   type1 item1;
   type2 item2;
   .
   .
}structure_variable;

#include <stdio.h>

struct book{
   char title[10];
   char author[20];
   double price;
   int pages;
};

int main(){
   struct book book1 = {"Learn C", "Dennis Ritchie", 675.50, 325};

   printf("Title:  %s \n", book1.title);
   printf("Author: %s \n", book1.author);
   printf("Price:  %lf\n", book1.price);
   printf("Pages:  %d \n", book1.pages);
   printf("Size of book struct: %d", sizeof(struct book));
   return 0;
}

Title:  Learn C
Author: Dennis Ritchie
Price:  675.500000
Pages:  325
Size of book struct: 48

union [union tag]{
   member definition;
   member definition;
   ...
   member definition;
} [one or more union variables];

#include <stdio.h>

union Data{
   int i;
   float f;
};

int main(){
   union Data data;

   data.i = 10;
   data.f = 220.5;

   printf("data.i: %d \n", data.i);
   printf("data.f: %f \n", data.f);
   return 0;
}

data.i: 1130135552
data.f: 220.500000

enum myenum {val1, val2, val3, val4};

#include <stdio.h>

enum status_codes { OKAY = 1, CANCEL = 0, ALERT = 2 };

int main() {
   // Printing values
   printf("OKAY = %d\n", OKAY);
   printf("CANCEL = %d\n", CANCEL);
   printf("ALERT = %d\n", ALERT);

   return 0;
}

OKAY = 1
CANCEL = 0
ALERT = 2

data_type *pointer_name;

pointer_name = &variable_name;

#include <stdio.h>

int main() {
   int x = 10;

   // Pointer declaration and initialization
   int * ptr = & x;

   // Printing the current value
   printf("Value of x = %d\n", * ptr);

   // Changing the value
   * ptr = 20;

   // Printing the updated value
   printf("Value of x = %d\n", * ptr);

   return 0;
}

Value of x = 10
Value of x = 20

malloc (size_t size);
calloc() Function

void *calloc(size_t nitems, size_t size)

void *calloc(size_t nitems, size_t size)

void *calloc(size_t nitems, size_t size)

#include <stdio.h>
#include <stdlib.h>

int main() {
   FILE *file;
   char file_name[] = "my_file.txt";
   char write_data[100] = "Tutorials Point";
   char read_data[100];

   // Opening file in write mode
   file = fopen("file_name.txt", "w");
   if (file == NULL) {
      printf("Error\n");
      return 1;
   }
   // Writing to the file
   fprintf(file, "%s", write_data);
   // Closing the file
   fclose(file);

   // Again, opening the file in read mode
   file = fopen("file_name.txt", "r");
   if (file == NULL) {
      printf("Error.\n");
      return 1;
   }

   // Reading data from the file
   if (fgets(read_data, 100, file) != NULL) {
      // Printing it on the screen
      printf("File's data:\n%s\n", read_data);
   }
   fclose(file);

   return 0;
}

File's data:
Tutorials Point

#define MAX_ARRAY_LENGTH 20