Computer Science 433
Programming Languages

Fall 2012, The College of Saint Rose

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Agenda

• Announcements
• First programming assignments due tonight
• Programming Language of the Day: C
  • See The Development of the C Language
• A crash course in C and Unix

Lecture Assignment 3

Due at the start of class, Monday, September 10.

Please submit answers to these questions either as a hard copy (typeset or handwritten are OK) or by email to terescoj AT strose.edu by the start of class. Please use a clear subject line when submitting by email (e.g., CSC 433 Lecture Assignment 3, Joe Student). We will discuss these questions at the start of class, so no late submissions are accepted.

1. (5 points) You have likely seen Java applications that take command-line parameters (the String args[] parameter to main). Write a C program that takes an arbitrary number of command-line parameters, each of which should represent an integer value. Print out the sum of the values provided. Call your C program argadder.c.

   Some things to know:

   • A C program that wishes to make use of command-line parameters must declare two parameters, traditionally named argc and argv.
   • The parameter argc to the main function is a count of how many command-line strings are included in argv, which is an array of strings. (See the main function in the gcd example.)
   • argv[0] is not the first parameter, it is the program name itself, and this array entry for the program name is included in the value of argc.
2. (10 points) Write a C program that reads in an integer (which must be at least 2) from the keyboard, then computes and prints out its prime factorization.
   • You need not store the factors. You may just print them out as they are determined, if this makes your program simpler.
   • Do error checking on the number entered. Repeatedly prompt for and read in values until you get a integer which is at least 2. You may find it helpful to note that the scanf function returns the number of successfully-matched tokens. If a call to scanf fails to find valid input, you may wish to follow it with a loop such as

         while (getchar() != '\n');
     

     to ignore any extraneous input on the same line as the invalid input that caused the scanf call to fail.

   • You may find it easier to write this program in a language you know well first to get the logic right, then convert to C.

Examples

• hello_c
• gcd
• matmult