CMPT 127 Spring 2019 Grade: / 20 First name: Last name: Student Number: Lab Exam 1 D400 1. [1 mark] Give an example of a sample input which would make the function scanf( "%f", &f ) return -1? Answer: EOF or CTRL + D 2. [3 marks] Circle the errors in the following program and write the correct/missing statements in order for the program to compile and execute. The program would then be executed with this command line statement:./a.out 99 4.567 #include <stdio.h> #include <stdlib.h> int main( int argc, char* argv[] ) { if ( argc!= 3 ) { printf( "I wanted 2 arguments!\n" ); else { int i = atoi( argv[1] ); float f = atof( argv[2] ); printf( "i = %n and f = %.2f.\n", i, f ); -> %d printf( "i = %n and f = %.2f.\n", i, f ); OR #include <stdio.h> #include <stdlib.h> int main( int argc, char* argv[] ) {
if ( argc!= 3 ) { printf( "I wanted 2 arguments!\n" ); else { int i = atoi( argv[1] ); float f = atof( argv[2] ); printf( "i = %n and f = %.2f.\n", i, f ); -> %d OR #include <stdio.h> #include <stdlib.h> int main( int argc, char* argv[] ) { int i; float f; if ( argc!= 3 ) { printf( "I wanted 2 arguments!\n" ); else { i = atoi( argv[1] ); f = atof( argv[2] ); printf( "i = %n and f = %.2f.\n", i, f ); -> %d 3. [2 marks] Write the compile command you would enter at the command line to compile the files test.c and stack.c such that all warning are turned on. Answer: gcc Wall test.c stack.c
CMPT 127 Spring 2019 First name: Last name: Student Number: 4. [2 marks] We have seen that the memory is divided in various segments. For example, the program's text (compiled code) is stored in the text segment. Which of these memory segments is used when we allocate memory space for a variable by calling malloc( )? Answer: heap 5. [2 marks] Where are the function declarations located when you write C programs? Hint: There are a few correct answers to this question and the Internet is not one of them. Answer: Some function declarations are located in the header files which are in the preprocessor include statements at the top of our C program in our code file. For example, #include <stdio.h>. Some function declarations (for the functions we implemented in our code file) are located above the function(s) (like the main function) which call(s) them. 6. [3 marks] Imagine there is a program that reads course marks (assignment marks, exam marks, etc ) and computes a student final mark for a particular course. Imagine also that, contrary to most of our tasks so far, the input to this program is not guaranteed to be well-formed. Your task in this question is to list two different sample input, and corresponding output, you would use in order to test this program to ensure it works no matter what data is entered. 1. Sample input: Well-formed input (valid input) such as 74 67 89 65 (we can assume that they are all out of 100) Sample output: Final mark: 73.75%
2. Sample input: Not well-formed input (invalid input) such as sausage Sample output: Sausage is not a number. Unable to compute final mark!
CMPT 127 Spring 2019 First name: Last name: Student Number: 7. [7 marks - Read the entire question first] Write a program called LabExam1.c which is to satisfy the following requirements: Use this incomplete main function as your starter program: #include <stdio.h> #include <stdlib.h> int main( void ) { int arraysize = 1024; int numofages = 0; int sum = 0; float theaverage = 0.0; int * arrayofages = getages( &numofages, arraysize ); // Add more code here free( arrayofages ); You are asked to write the function getages which must 3. Allocate an array of arraysize of integers. 4. Fill this array with ages read from standard input, i.e., integers entered at the command line, separated by one or more spaces or newline characters, until EOF is reached, and 5. Return the number of ages read via the parameter numofages. It also returns the array as the returned value, which is then assigned to arrayofages. 6. To keep the problem simple, you can assume that only integers, spaces and newline characters will be entered at the command line to test your program. This is to say that no other characters will be entered such as punctuation, letters, etc
7. On reaching EOF, the getages function returns to the main function which must then calculate the average of the ages contained in arrayofages and print to stdout the number of ages read, the sum of these ages and their average (as well as a newline character \n ) using a format that will produce the exact format exemplified in the samples outputs below: 8. Sample input 1 - Assuming the executable is called le1: $./le1 25 57 78 12 45 <- sample input # of ages: 5, sum of ages: 217, age average: 43 <- sample output $ 9. Sample input 2 - Assuming the executable is called le1: $./le1 <- sample input # of ages: 0, sum of ages: 0, age average: 0 <- sample output $ When adding code to the main function, you can only do so after the call to the getages function in the main function, i.e., where it says // Add more code here. You cannot change the code you have been given above. Make sure your code file LabExam1.c compiles and executes as expected. When it does, submit it to CourSys before or at the end of your lab exam. Remember, late submissions will get 0. Suggestion: Implement small sections of your LabExam1.c at a time, then compile it, test it and submit it to CourSys. Repeat this until you have implemented your entire LabExam1.c. Know that you can submit your file many times to CourSys. Also know that only the last submission will be marked. Good luck!
CMPT 127 Spring 2019 First name: Last name: Student Number: /* Lab Exam 1 - Q7 - D400 */ #include <stdio.h> // for printf() #include <stdlib.h> // for atoi() int * getages( int * numofages, int asize ) { int result = 0; unsigned int index = 0; int d = 0; // explicitly allocate space for an array of ints int * anarray = malloc( asize * sizeof(int) ); // always check a system call for errors if( anarray == NULL ) { perror( "Allocating an array of size asize failed!" ); exit(1); *numofages = 0; // fill array read ages while ( ( result = scanf( "%d", &d ) )!= EOF ) { if ( d!= '\n' && d!= ' ' ) anarray[index++] = d; // return the number of ages read *numofages = index; return anarray; int main( void ) { int arraysize = 1024; int numofages = 0; int sum = 0; float theaverage = 0.0; int * arrayofages = getages( &numofages, arraysize ); // running sum for (unsigned int i = 0; i < numofages; i++) { sum += arrayofages[i];
// if at least one age has been read, compute average if ( numofages > 0 ) theaverage = sum / numofages; // print stats printf( "# of ages: %d, sum of ages: %d, age average: %.0f\n", numofages, sum, theaverage ); // de-allocate the memory allocated by malloc free( arrayofages );