EECS2031-LAB 1 Solved

Introduction to C, Function Declaration vs. Definition, Basic I/O (scanf/printf, getchar/putchar, input/output redirection) 

 
1 Problem A.  scanf, printf
 

1.1  Specification
Write an ANSI-C program that reads input from the Standard Input, and then outputs the reformatted versions of the input.

 

1.2 Implementation
You can download the file hello.c and use it as a template.

•       name your program lab1A.c 

•       use scanf to read input (from Standard Input), which are in the form of   Month Day  Year (i.e., three integers  separated by white spaces).

•       use printf to generate output in the format of Year/month/day and Year-monthday

•       display the following prompt (leave a white space after the colon)

Enter month, day and year separated by spaces: 

•       display output as follows (white space between each word): 

   The input 'x xx xxxx' is reformatted as x/xx/xxx and x-xx-xxx 

 

•       Note: you should do the reformatting only within printf. In particular, you should use at most three variables, and feed them into  printf judiciously.  

 

1.3 Sample Inputs/Outputs: 

red 306 % gcc lab1A.c red 307 % a.out 

Enter month, day and year separated by spaces: 3 20 2019 The input '3 20 2019 ' is reformatted as 2019/3/20 and 2019-3-20 red 308 % 

 

2 Problem B.   Functions in C
  

Download the program lab1B.c, compile it using  gcc lab1B.c  

Observe that the compilation process fails (why?), and a.out is not generated.

 

Modify the program to make it compile. Note that you should not modify or move the existing code. That is, do not modify the code of main() and  sum(), and also do not move the functions.  

Instead, add something to make it compile.  

Run the program to see the output.

 
3 Problem C.  Functions, scanf, printf, floats
 

3.1 Specification
Improve program lab1B, so that it can read two float numbers for the Standard Input, separated by two pound (#) signs, and then output the sum of the two float numbers.  

 

3.2 Implementation
•       name your program lab1C.c 

•       use scanf to read inputs (from Standard Input), which are in the form of float1##float2 (i.e., two float numbers separated by two pound signs).

•       use printf to generate output

•       display the following prompt (leave a white space after the colon):

Enter two float numbers separated by ##: 

 

3.3 Sample Inputs/Outputs:  (notice that by default printf displays six digits after decimal points of a floating point number.)

red 338 % gcc lab1C.c  -o lab1C 

red 339 % lab1C 

Enter two float numbers separated by ##: 2.35##5.64 

2.350000 + 5.640000 = 7.990000 red 340 %  

 

4 Problem D.   Simple loops
 

4.1 Specification
Extend program lab1C, in such a way that it first prompts the user to enter an integer number, which indicates how many times the user wants to interact with the program. Then the program interacts with the user accordingly.

 

4.2 Implementation  
•       name your program lab1D.c 

•       use a loop (for or while) to interact (i.e., read  input and generate output)  n times, where n is entered by the user.  

 

4.3 Sample Inputs/Outputs: (ONE blank line between each interaction/iteration): 

red 338 % gcc lab1D.c  -o lab1D 

red 339 % lab1D 

Enter the number of interactions: 3 

 

Enter two float numbers separated by ##: 2.35##5.64 

2.350000 + 5.640000 = 7.990000 

 

Enter two float numbers separated by ##: 1.1##2.2 

1.100000 + 2.200000 = 3.300000 

 

Enter two float numbers separated by ##: 2.5##6 

2.500000 + 6.000000 = 8.500000 red 340 %  

Submit your program using submit 2031Z lab1 lab1D.c 

 

5. Problem E.  getchar, putchar, input/output redirection
 

5.1 Specification
Download the provided program copy.c, which uses getchar and putchar to read user input from Standard input (keyboard) and write the input to Standard output (screen). (This program is also in the textbook and the lecture slides.)

Play with the program and make sure you understand the program. In particular, observe a few things about getchar and putchar:

•       getchar() returns  EOF  (which is a special negative number defined in C)  when the “end of file” is reached.  

o If the program reads from a text file (redirected using < ), then the end of the text file is

“end of file”;  o If the program reads from Standard in (i.e., keyboard) , then in Unix, ctrl D indicates “end of file”  (in Windows, it is ctrl Z )

•       Although the program calls putchar after every getchar, you will notice that the output is displayed only after a whole line is read in. This is correct and is related to the buffer used by the system. Specifically, instead of executing putchar for every getchar, the system buffer stores the chars that are read in, and executes putchar only after a new line character '\n' is read in.

•       Instead of a char, function getchar returns an int, and putchar takes as argument an int.  This will be explained in class.

 

5.2 Sample Inputs/Outputs (from Standard input  -  keyboard): 

red 308 % gcc copy.c red 309 % a.out hello hello how are you! how are you! 

I am good and thanks ! 

I am good and thanks ! ^D (press Ctrl and D) red 310 % 

5.3 Sample Inputs/Outputs (use redirected input/output files): 

 

You can always redirect the Standard in (keyboard) from an input file using  < You can always redirect the Standard out (screen) to an output file using  > 

 

Download file greetings.txt,whose content is

hello how are you 

I am good  

red 311 % a.out < greetings.txt hello how are you I am good 

red 312 % a.out  < greetings.txt > output.txt 

 

Nothing will be generated on the screen, because output is redirected using > .  Now a new file output.txt should be generated (in the current directory). Use command ls or ls –l to confirm this. Then use command cat or more to view the content of output.txt  (If you don’t know what is happening here, please review the CSE1020 lab tour posted on the course website).

 red 313 % ls -l red 314 % cat output.txt  hello how are you 

I am good 

 

You don’t need to submit anything for this question but doing this gets you prepared for the next questions.

 

 

6. Problem F  getchar, character comparsion
 

6.1 Specification
In class we showed a simple program that uses getchar to read input character by character, counting the number of characters from the standard input (keyboard or directed).  

Note that this program counts new line characters.  

Modify the program so that it counts only visible characters, i.e., new line character is not counted.  

 

6.2 Implementation  
•       Hint: you might need to compare what getchar reads in against the new line character. Note that like in Java or C++, comparing characters are easy. You can compare characters using relational operator == directly, (although you cannot use == to compare "strings"). We will talk about this in the next class.

•       Name your program lab1F.c 

 

 

6.3 Sample Inputs/Outputs red 308 % gcc lab1F.c –o lab1F red 309 % lab1F hello how are you 

I am good 

^D (press Ctrl and D) # of chars:  25 red 310 % red 311 % a.out < greetings.txt 

# of chars:  25 red 312 % a.out  < input.txt > outputF.txt 

 

If your program runs correctly, a new file outputF.txt should be generated (in the current directory). Use command ls or ls –l to confirm this. Then use command cat or more to view the content of it. red 313 % ls -l red 314 % cat outputF.txt  

# of chars:  25 

 

7. Problem G   getchar, character comparsion
Modify the program lab1F.c  so that it also counts the number of lines in the input.   

Name your program lab1G.c 

 

red 308 % gcc lab1G.c –o lab1G red 309 % lab1G hello how are you 

I am good 

^D (press Ctrl and D) 

# of chars:  25 # of lines:  3 

red 310 % lab1G < greetings.txt 

# of chars:  25 # of lines:  3 

red 311 % lab1G < greetings.txt > outputG.txt red 312 % cat outputG.txt 

# of chars:  25 

# of lines:  3 
 

Common Notes
All submitted files should contain the following header:

/*************************************** 

*  Filename: Name of file * 

*  Author: Last name, first name * 

*  Email: Your EECS email address * 

*  eecs_username: Your eecs login user name * 

*  York Student #: Your student number 

****************************************/ 

 

In addition, all programs should follow the following guidelines:

•       Include the stdio.h library in the header of your .c files.  

•       Assume that all inputs are valid (no error checking is required, unless asked to do so). 

 

You are also encouraged to  

•       Give a return type int for main(), and return 0 at the end of main()  

•       Specify parameters for main() function, as main(int argc, char *argv[])