Lab 2: Pointers and Input Solution

Introduction




The purpose of this lab is to practice writing C programs involving pointers and the scanf function.







To start, log in to MarkUs and navigate to the lab2 assignment. Like the previous lab, this triggers the starter code for this lab to be committed to your repository. We've described each problem briefly below, but for more detail on the first two problems, read through the starter code. There is no starter code for the final two problems.







1. invest.c




Your task is to implement a function invest that takes an amount of money and multiplies it by a given rate. It's your job to figure out the exact type of this function's arguments, given the sample usage in the main function in the starter code.







2. score_card.c




Your task is to implement a function sum_card , which takes an array of pointers to integers, and returns the sum of the integers being pointed to.







3. phone.c




Your task is to write a small C program called phone.c that uses scanf to read two values from standard input. The first is a 10 character string and the second is an integer. The program takes no command-line arguments.







If the integer is -1, the program prints the full string to stdout. If the integer is between 0 and 9 the program prints only the corresponding digit from the string to stdout. In both of these cases the program returns 0.




If the integer is less than -1 or greater than 9, the program prints the message "ERROR" to stdout and returns 1.




We haven't learned about strings yet, but you will see that to hold a string of 10 characters, you actually need to allocate space for 11 characters. The extra space is for a special character that indicates the end of the string. Use this line







char phone[11];




to declare the variable to hold the string. Other than this line, there is no starter code for this program.




Note: the program must not print any prompts.




4. phone_loop.c




Your task is to write a C program called phone_loop.c . This program will again read from standard input using scanf and take no command-line arguments. Similar to phone.c , this program reads a 10-character string as the first input value but then it repeatedly reads integers until standard input is closed.







After each integer the output produced is as before:




if the integer is -1, the full string is printed







if the integer is between 0 and 9, the individual character at that position is printed







if the integer is less than -1 or greater than 9, the message "ERROR" is printed (to stdout)







https://q.utoronto.ca/courses/130688/assignments/243359 1/2
4/15/2020 Lab 2




In each case the printing is followed by a newline character.




When the program finishes running, main returns with a 0 return code if there were no errors and with a 1 return code otherwise.







Note: the program must not print any prompts.




How do you end standard input?




One way to run your program is to redirect the input to come from a file. Then it is clear when the file ends. But how do you close standard input, when it is coming from the keyboard? You manually indicate the end of standard input from a keyboard by pressing Ctrl-D (on Unix) or Ctrl-Z (on Windows) and enter.




Submission




Use git to submit your final invest.c , score_card.c , phone.c and phone_loop.c -- make sure they're inside your lab2 folder and named exactly as described in this handout, as that's where our test scripts will be looking for them. Do NOT add or commit executables to your repository. We will build executables by compiling your code as part of testing it.







IMPORTANT: make sure to review how to use git to submit your work to the MarkUs server; in particular, you need to run git push , not







just git commit and git add .























































































































































https://q.utoronto.ca/courses/130688/assignments/243359 2/2