APS 105F - Computer Fundamentals

Assignment #9:  The C Programming Language

Fall 1997

(To be completed on Nov. 12/13)

 

Objective:   To learn the basics of C programming

Example C programs and a makefile can be found in the directory /usr/copy/aps105/Csamples on ECF.

1 A Grades Classification Program

A good way to start with a new language is to translate from one that you know. If you have been using C all along, then treat this as pseudo-code.

The following Turing program will read a sequence of grades (integers in the range of 0-100 inclusive), terminated with a negative number. It will then print out the number of grades in each of a number of ranges, and the class average (mean grade). You should study this program so that you understand its operation, and then rewrite it in C. You should create a simple makefile and demonstrate how to use it to compile your program. Test your program thoroughly. Note that for an empty input sequence, no output should be given.

        var b1,b2,b3,b4,b5,b6: int:= 0
        var grade: int
        var gradeCount: int:= 0        % number of grades
        var total: int:= 0             % accumulator
        put "Enter grade (end with -1) " ..
        get grade
        loop        % ... while grade >= 0 do ...
          exit when grade < 0
          gradeCount:= gradeCount + 1
          total:= total + grade
          if grade < 50 then
            b1:= b1 + 1         % grades below 50
          elsif grade < 60 then
            b2:= b2 + 1         % grades 50-59
          elsif grade < 70 then
            b3:= b3 + 1         % grades 60-69
          elsif grade < 80 then
            b4:= b4 + 1         % grades 70-79
          elsif grade < 90 then
            b5:= b5 + 1         % grades 80-89
          else
            b6:= b6 + 1         % grades 90-100
          end if
          put "Enter grade (end with -1) " ..
          get grade
        end loop
        if gradeCount > 0 then
          put b1, " is/are below 50"
          put b2, " is/are in range 50-59" 
          put b3, " is/are in range 60-69" 
          put b4, " is/are in range 70-79" 
          put b5, " is/are in range 80-89" 
          put b6, " is/are in range 90-100" 
          put "The average is ", total/gradeCount
        end if

2 Sorting

Write a C program that reads in a sequence of positive integers and outputs them in sorted order using the bubble sort algorithm. The sequence is terminated with the number -1, which is not to be part of the sequence. Assume that there are at most 20 numbers to be entered, not including the -1.

3 Optional

Change your sorting program so that it inputs and sorts words instead of numbers. The list of words should terminate with the word ``end.''

Since C does not have builtin string handling, a standard library of string handling functions has been developed. To access it, you will have to have #include <string.h> at the top of your program. You can see what these commands are by typing man string.