Due by 11:59.59pm Sunday, September 24, 2017
In this lab you will get experience dealing with data on the binary level. You will also have to deal with static local variables and using global variables. In addition, you'll be expected to use conditional compilation via a Makefile, creating header files, etc.
You may work with a partner on this assignment. If you choose to do so, it is expected that you work together and equally contribute to the development of your solution. Also, you are both responsible for understanding how your solution works. You need only submit one assignment per group, but clearly indicate your partnership in the README and comments for files. You should play with collaborating on github as you are doing this.
The URL for the github repository for this account is https://classroom.github.com/a/mTKsZteU
In this part, we will start using arrays to contain frequencies of characters and print a summary of a text's character distribution.
In C, an array is defined as
int arr[LENGTH];where LENGTH must be a constant. Typically, we will declare something like
#define LENGTH 256somewhere in our program before we define the array. Note, you cannot use a variable for the array length. It must be something that is evaluated at compile time, not at run-time.
Your assignment is to create a program that has an array of all possible lowercase characters (a-z). Your program will read from stdin, like the programs last week, and count how many times each letter has occured.
You will then print out, in tabular form, the letter, the number of times that it has appeared, and the percentage of all letters that this letter represents. Following this table, print out which is the most frequent and least frequent letter. If there are multiple letters that are most or least frequent, you should print them all out in sequence.
An example run is as follows, using the file "hamlet.txt" located in ~rhoyle/pub/cs241/hw02/hamlet.txt
rhoyle:hw2 rhoyle$ ./freq < ~/Downloads/hamlet. char Frequencies Percentage a: 9950 7.6459 b: 1830 1.4062 c: 2606 2.0025 d: 5025 3.8614 e: 14960 11.4958 f: 2698 2.0732 g: 2420 1.8596 h: 8731 6.7092 i: 8511 6.5401 j: 110 0.0845 k: 1272 0.9774 l: 5847 4.4930 m: 4253 3.2681 n: 8297 6.3757 o: 11218 8.6203 p: 2016 1.5492 q: 220 0.1691 r: 7777 5.9761 s: 8379 6.4387 t: 11863 9.1159 u: 4343 3.3373 v: 1222 0.9390 w: 3132 2.4067 x: 179 0.1375 y: 3204 2.4621 z: 72 0.0553 Maximum character(s): E Minimum character(s): Z
In this part, you will be creating 2 programs. encode_bits which will generate the "binary" representation of a file and decode_bits which will take that representation and convert it back to the original format.
Create a program called encode_bits. This program should use getchar() to read in characters one at a time and then call print_bits() (see below) to output that character as a sequence of '1' and '0' characters. It should stop on EOF.
Create a program called decode_bits. This program should use getchar() to read in characters one at a time and then call decode_bits() (see below) to output that sequence of '1' and '0' characters as actual characters. It should stop on EOF.
Create a file called bits.c that contains the following two functions and a header file bits.h that contains a guard against multiple inclusion, other needed includes, and function prototypes.
You'll probably need to use static local variables to handle decode_bits since it only prints out a character every CHAR_BIT calls to it.
Don't forget to make rules in your Makefile include the correct compilation. bits.o should be the dependency for the two other programs, and you should have a separate rule for its compilation.
For the second part, you will be creating a function to read in a signed integer value and storing the result in a long integer variable. You will also be creating 4 short programs that will use that function to read in integers and output them in one of 4 different formats -- binary, decimal, octal, or hexadecimal.
Create a file called getnum.c and another called getnum.h. In getnum.c you will create the function getnum() that is used by your other programs.
You will then create 4 short programs that will read in a sequence of number and then output them one per line in a specified format. All 4 will be using sign-magnitude format. (If negative, print out the sign and then the rest as if it were positive -- important for binary.)
In the event that the integer being read is invalid, simply print "ERROR" to the screen.
Loop until no more integers remain.
Don't forget to add these targets into your Makefile.
I've included my sample solution in ~rhoyle/pub/cs241/hw04/ with binaries that should work on the lab machines.
decode_bits should exactly undo encode_bits. For example, you should get no output from the following:
% ./encode_bits < ./encode_bits | ./decode_bits > output % diff -q encode_bits output
You can also chain together the base transformation if you like
% echo -32767 0xffff 071 0b101 cat | ./tobinary | ./tohex | ./tooctal | ./todecimal -32767 65535 57 5 ERROR
Read in a flag on the command line that specifies the base for the output. It should be one of:
Note, your output, if octal, should be the regular number without the leading 0. The number, if hex, should be the regular number without the leading 0x. You will need to modify both encode_bits and decote_bits for full credit, as you'll need to be able to decode each type of encoding.
As with the first project, I want you to create a file called README
I have adhered to the Honor Code in this assignment
Now you should make clean to get rid of your executables and commit your folder containing your source files, README, and Makefile through git, as you did in last week's assignment. For a refresher, refer to those instructions.>
Here is what I am looking for in this assignment: