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Tom Kelliher, CS 320

Jan. 26, 2005

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Assignment

Read 1.1--4.

Outline

1. Syllabus.

2. Terminal I/O in C.

3. Accessing command-line arguments.

Coming Up

Structures, pointers, and memory allocation in C

Syllabus

Terminal I/O in C

1. printf

   #include <stdio.h>
   
   int main()
   {
      /* Variable declarations must occur at the _start_ of a block. */
      int sum = 12;
      double min = 0.1, max = 5.5;
      char name[] = "Tom Kelliher";
   
      printf("I am a constant string.\n");
   
      printf("The sum is: %d\n", sum);
   
      printf("Min is: %g.  Max is: %g.\n", min, max);
   
      printf("Your name is %s.\n", name);
   
      return 0;
   }
   

   Refer to printf(3C) on phoenix. (man -s 3C printf)

2. scanf

   #include <stdio.h>
   
   int main()
   {
      int i, age;
      double weight;
      char name[80];
   
      printf("Enter your age: ");
      scanf("%d", &age);
      printf("You entered %d.\n", age);
   
      printf("Enter sample weight: ");
      scanf("%lg", &weight);
      printf("You entered %g.\n", weight);
   
      printf("Enter your name: ");
      scanf("%s", name);
      printf("Your name is %s.\n", name);
   
      /* Eliminate whitespace following previous name. */
      while (getc(stdin) != '\n')
         ;
   
      printf("Enter your name: ");
      fgets(name, 80, stdin);
   
      /* Eliminate the newline following name */
      i = 0;
      while (name[i] != '\n')
         i++;
   
      name[i] = '\0';
   
      printf("Your name is %s.\n", name);
   
      return 0;
   }
   

   Refer to scanf(3C).

Command-Line Arguments

1. Command-line arguments in Unix:

   foo arg1 arg2 arg3
   

2. Command-line arguments in Visual C++: Open Project menu, choose Settings, choose Debug tab, enter arguments on Program Arguments line.

3. Example:

   #include <stdio.h>
   #include <stdlib.h>
   
   int main(int argc, char *argv[])
   {
      int sum, current, i;
   
      if (argc <= 1)
      {
         printf("No arguments!\n");
         return 1;
      }
   
      sum = 0;
      for (i = 1; i < argc; i++)
      {
         current = atoi(argv[i]);
         sum += current;
         printf("Arg %d: %d\n",  i, current);
      }
   
      printf("\nThe sum is %d.\n", sum);
   
      return 0;
   }
   

Practice

1. Creating a console application in Visual C++:
   1. Open the File menu and select New.

   2. Select Win 32 Console Application, fill-in Project Name and Location (folder).

   3. Select An empty project.

2. Creating new source files: Open the File menu and select New. Choose either the C/C++ Header File or C++ Source File. Fill-in a file name (no extension).

3. Practice program: Write a C program which accepts exactly three integer command-line arguments and prints the largest of them.