2005 Introduction to Computer Programming

Sample Codes

Sample 1: Your First C Program - Hello World.

// header file
#include <stdio.h>
#include <stdlib.h>

int
main()	// function main begins program execution
{
	printf("Hello World\n");	// print a line of "Hello World" on the screen 
	return 0;			// indicate that program ended successfully
}

Result:

Hello World

Sample 2: printf & scanf

//header file
#include <stdio.h>
#include <stdlib.h>

int
main()  // function main begins program execution
{
	int a;
	printf("Please enter a integer: ");
	scanf("%d", &a);
	printf("An integer is %d.\n", a);
	return 0;
}

Result:

Please enter a integer: 14
An integer is 14.

Sample 3: Palindrome - word or phrase that reads the same backwards as forwards

//header file
#include <stdio.h>
#include <string.h>	//strlen的定義在這裡頭

int
main()
{
  char string[1000];
  int i, j, len;
  int flag = 1;
  
  printf("Please input a string: ");
  scanf("%s", string);

  len = strlen(string);	//傳回字串長度
  
  for(i = 0, j = len -1; i < j; i++, j--)
  {
    if(string[i] != string[j])
      flag = 0;
  }
  
  if(!flag)
  {
    printf("%s is not a palindrome\n", string);
  }
  else
  {
    printf("%s is a palindrome\n", string);
  }
}

Result:

Please input a string: abbbcbbba
abbbcbbba is a palindrome

Sample 4: Read and Write Text File

//header file
#include <stdio.h>
#include <string.h>	//strlen的定義在這裡頭
#define MAX 65500

int
main()
{
  FILE *fp, *fp2;
  char infile[MAX];
  char outfile[MAX];
  char buffer[MAX];
  
  printf("Please input a input file name: ");
  scanf("%s", &infile);
  printf("Please input a output file name: ");
  scanf("%s", &outfile);

  fp = fopen(infile, "r");
  fp2 = fopen(outfile, "w");
  
  if(!fp && !fp2)
  {
    printf("File not found!");
    exit(0);
  }
  
  while(fgets(buffer, MAX, fp) != NULL)
  {
    buffer[strlen(buffer) - 1] = '\0';
    
    fprintf(fp2, "%s\n", buffer);
  }
  
  fclose(fp);
  fclose(fp2);
}