Caesar Encryption and decryption C++

Question

I would like to know how to limit the ASCII range of encryption from 32 - 126.

For our task we are supposed to convert string to char and encrypt/decrypt each individual char.

I'm currently using this for encryption

int value = (value-32+shift)%95+32 //value is the current ascii value of a                 
                                   //character
                                   //the first shift is given by the user with regards 
                                   //to how many shifts he wants to do to the right

and this for decryption

int value = (value-32-shift)%95+32

my encryption is working perfectly (when I quote out the decryption function) but my decryption is not working how it is supposed to.

extra note: We only have to do a right shift when encoding, a single string is given for our entire program to encrypt and decrypt ("This is C++")

Give shift: 3
Wklv#lv#F..
DECODE 
Wklv#lv#F..  //must be 'THIS is C++'
ENCODE       //shift=15
This is C++  //must be 'cwx#/x#/R::'  
DECODE 
EYZdpZdp4{{  //must be 'THIS is C++'
ENCODE      //shift=66
cwx#/x#/R::  //must be "8LMWbMWb'mm"
DECODE 
This is C++
ENCODE       //shift=94
cwx#/x#/R::  //must be 'SGHR~hr~B**'
DECODE 
This is C++

Note: in process of adding more code description

Answer 1

Your problem is explained in Modulo operator with negative values. I'm not sure this is an exact duplicate. The problem is that decoding a cipher character like '!' with a shift of more than one (say "3")

int value = (value-32-shift)%95+32
          = ('!'-32-3)%95+32
          = (33-32-3)%95+32
          = (-2)%95 + 32
          = -2 + 32
          = 30

Oops. You need to use:

int value = (value-32+(95-shift))%95+32