Question

How to make a Caesar C program? More like, how to use isupper(), islower(), and how to translate the plaintext into ciphertext?

Answer 1

@e.mccormick

Answer 2

Well, you knw the basis of the Ceasar cyper, shifting text, right?

Answer 3

Not really- I know what functions to use, but I don't know how to use them :C
But I know the loops, how to use them, and the normal C stuff like the header files, brackets, etc.

Answer 4

I can show you what I've got so far. Do you want me to show you?

Answer 5

I do not mean the computer part, I mean the Ceasar part.

Answer 6

OHHHH!!!! Yeah I know it. Lol I was so confused when you said shifting text XD

Answer 7

You're an awesome mod. :) Thanks for helping me! :D

Answer 8

I hope you hit 2015 fans C:

Answer 9

By the way it is Caesar not Ceasar lol I get it mixed up too

Answer 10

I do not care about the Latin spelling. I have enough trouble with English. =P

OK. So, the isupper and islower stuff just return if a character is upper case or if it is lower case. They return true or false.

Answer 11

:P

Answer 12

Typically, what you would use the upper/lower for in a C-Cypher is to see what range of characters you need to shift.

Answer 13

Ok so here is my problem with those. I know what they do, but I don't really know how to use them correctly. I'm using the command line argument thing - my first line of real programming is
int main(int words, string letters[])

So I keep getting argc and argv confused. How do I like... call... on the xth letter of the yth command line argument?

Answer 14

A-Z is 65 to 90
a-z is 97 to 122

You need to find out if a letter is a capitol or lower case so you know if you need to shift it around in the 65 to 90 range or in the 97 to 122 range.

Answer 15

Yea i know that stuff... But not much other than that =P

Answer 16

The command line stuff makes an array.

Answer 17

http://www.asciitable.com/ Right now I'm thinking of using the isupper/islower functions like this:
if isupper is true
asciivalue-65+key

above thing+65, convert to char
same way with islower, but then -97

Answer 18

Just remember to pass it through a modulo. That will wrap it around if you pass z.

Answer 19

Oh yea ok I got that. Thanks :)

Answer 20

How comand line arguments work:
http://www.tutorialspoint.com/cprogramming/c_command_line_arguments.htm

Answer 21

Currently Uploading a video to show you my program.

Answer 22

http://screencast-o-matic.com/watch/coeuc0eNl3 here. Please mute idk what got recorded :

Answer 23

A helpful link I'm using :) Maybe you can use it to help others! https://reference.cs50.net/

Answer 24

See, the problem with int main(int words, string letters[]) is that it is not really accurate.

The main uses that for the command line arguments. The int is the number of arguments and will always be at least 1. The string or character array is the list of whitespace separated list of the arguments. The 0th position, or 1 aregument, that always exists is the name of the program. The 1st position is the first argument, and so on.

Answer 25

well im doing this for a course, and im pretty sure i have to use int main(int words, string letters[])

Answer 26

http://cdn.cs50.net/2015/x/psets/2/pset2/pset2.html#hail_caesar Here my eyes hurt :C

Answer 27

Well, if they want it called that, fine. It makes little sense... but oh well.

Answer 28

lol

Answer 29

So where exactly are you having a problem?

Answer 30

A few things. how to summon a certain letter of a word of a command line argument, and how to summon a certian word of a command line argument.

Answer 31

and how to use the isupper function correctly. do i put it in an if function statement, or do i use it as its own function

Answer 32

The string array hold the program name then any other arguments. So each one of those is a string. Getting the character out of a command line generated string is no different than from any other string.

Answer 33

When I use
int main(int words, string letters[])

How do I get the i'th word of the command line argument? I'm pretty sure it has some square brackets [] but i don't know which one to use and where everyting goes i too stupid

Answer 34

letters[0] = the name of the program
letters[1] = the first argument after the name of the program
letters[2] = the second argument after the name of the program
etc.

Answer 35

That's exactly what I needed... What about the letters inside ?

Answer 36

Are you sure these are C strings? Looks like C++...

Answer 37

100 percent sure its C.

Answer 38

Then how are you able to use the string class?

Answer 39

Idk

Answer 40

int main(int words, string letters[]) <--- that right there is a C++ string.

Answer 41

Well I didn't know that. but I'm certain that this is C.

Answer 42

They are probably loading a library.

Know about 2 dimensional arrays?

Answer 43

Yea

Answer 44

Well, yo have a string array of strings and each string is an array of characters. So try things like:

letters[1][0]

Answer 45

Where do i write this

Answer 46

Well, if you look at that, it sould be the first character of the first commmand line argument.

Answer 47

Sorry I'm lost..

Answer 48

A string is an array of characters.

The command line arguments are an array of strings.

In a 2d array, the first [ ] references the position within the outer array and the second [ ] is the position in the inner array.

So, liest say my array is this:

string words = {"One", "Two", "Three"}

Then, the following is true:

words[0] is One
words[1] is Two
words[2] is Three

But what if I want to get into one character? Well, then I need to use the 2d aspects:

words[0][0] is O
words[0][1] is n
words[0][2] is e

Answer 49

oh okz i gets it

Answer 50

Alo

Answer 51

that was a long break xD where u go?

Answer 52

Nowhere.

Answer 53

why u dont respond lol

Answer 54

"oh okz i gets it"

That seemed like you were fine. I saw nothing else to respond to. Also, moderators tend to sit wherever they were last while they deal with reports, etc.

Answer 55

Oh ok lol sorry I meant I understood what u said but i still dont know

Answer 56

What do you not know?

Answer 57

how to summon a letter im pretty sure its something simple like the words thing...

Answer 58

The math chat's time is messed up.

Answer 59

1 message is sent at 9 16, then another one after it is 9:12, then a 9 13,

Answer 60

That was it. What you said you understood was it. How I got the O out of One that was part of One Two Three.