A rubric for programming assignments

Transcription

1 Fall 2012 Comp 162 Peter Smith A rubric for programming assignments Generally, half the points for a program assignment are for the Correctness of the program with respect to the specification. The other half are split between Readability and Testing. The split will vary depending on how much testing is appropriate for the particular assignment. Here is an approximate rubric for the points followed by three example programs showing how each might be graded. Correctness (0 points) 0 Program is correct in form and function meets specification Program output is correct but elements of specification missing, e.g. parameter passing is missing 3 Program gives correct output in some but not all cases. For example, a program to find the largest number input does not work if all the inputs are negative 2 Part of the specification has been implemented, e.g. one out of two required subprograms. Program has elements of correct code but does not assemble/compile. Readability (2 points varies) 2 Programmer name and assignment present. Sufficient comments to illustrate program logic. Well-chosen identifiers. 1 Programmer name present, most sections have comments. Fair choice of identifiers Few comments, non-meaningful identifiers 0 No programmer name. No comments. Poor identifiers Testing (2 points varies) 2 Complete test cases run 1 Most test cases tried. One or two test cases run 0 No testing turned in or testing does not match program listing. The following three Pep/8 programs might have been turned in for the following assignment. Write a program that reads N followed by N integers X 1.. X N. After the last X is input the program prints the largest X value or an appropriate message

2 Program 1 Comp 162 A. Person Program reads N followed a set of N integers. After input is complete it outputs the largest of the set or an appropriate message. N:.block 2 for size of data set Number:.block 2 to hold a number in the set Largest:.block 2 to hold the largest so far. prompt:.ascii "Enter N: \x00" badinput:.ascii "N must not be negative\n\x00" label:.ascii "The largest number is: \x00" emptyset:.ascii "Set is empty, no largest number\x00" main: stro prompt,d deci N,d size of data set brge continue stro badinput,d if negative, output an error message and get another N continue: breq empty N is zero, set is empty so no largest ldx N,d deci Largest,d first number in the set is the largest so far subx 1,i breq done exit if N was 1 loop: deci Number,d enter a set member lda Number,d cpa Largest,d is it a new biggest? brlt skip skip if not sta Largest,d otherwise update the largest so far skip: subx 1,i more numbers to input? done: empty:.end brgt loop branch if so stro label,d deco Largest,d otherwise output the largest stro emptyset,d message if set size is zero Testing Enter N: 0 Set is empty, no largest number Enter N: 1 The largest number is: Enter N: The largest number is: 20 Enter N: 2 20

3 10 The largest number is: 20 Enter N: The largest number is: -000 Enter N: The largest number is: Scoring for this program Correctness 0/0 special cases accounted for Readability 20/20 good comments and variables and program layout Testing 27/30 Negative N checked for in program but not tested. Total 97

4 Program 2 Comp 162 B. Person N:.block 2 for size of data set Num:.block 2 to hold a number in the set L:.block 2 to hold the largest so far. prompt:.ascii "Enter N: \x00" badinput:.ascii "N must not be negative\n\x00" label:.ascii "The largest number is: \x00" main: stro prompt,d deci N,d size of data set brlt main get another one if user input negative ldx N,d loop: deci Num,d get a set member lda Num,d cpa L,d is it a new biggest? brlt skip skip if not sta L,d otherwise update the largest so far skip: subx 1,i decrease count of numbers to read brgt loop branch if more to read done: stro label,d deco L,d otherwise output the largest.end Testing Enter N: - Enter N: -3 Enter N: -2 Enter N: The largest number is: Enter N: The largest number is:

5 Scoring for this program Correctness 3/0 Uses zero for initial value of L so does not work if all inputs are negative. If zero entered for N still expects input of a set number and assumes set size is 1 Readability 1/20 Program specification not included what is program supposed to do? Identifiers could be better. Blank comment lines can be used to break up text. Testing 18/30 A set with only negatives would have revealed error. Test special cases N=0 would have revealed error. What about N=1 to verify that it works for that case? Mix positive and negative in the set? Total 67

6 Program 3 Comp 162 N:.block 2 Num:.block 2 L:.block 2 main: deci N,d Get N ldx N,d loop: deci Num,d get a set member lda Num,d cpa L,d see if bigger than L brgt skip sta L,d update L skip: subx 1,i brge loop branch for more done: deco L,d output the largest.end Testing Scoring for this program Correctness 18/0 Assumes user will input N > 0. Comparison with L followed by wrong branch instruction Goes round loop once too many times Uses zero for initial value of L If zero entered for N still expects input of a set number and assumes set size is 1 Readability 8/20 Whose program is this? Program specification not included what is program supposed to do? Identifiers could be better. Blank comment lines can be used to break up text. Comments add little to instructions

7 No prompt for N or label on output of largest Testing 12/30 Minimal. Does reveal errors though. Few different N values tried Total 38