encrypt.cpp:

#include #include #include "encrypt.h$"//$ Function to shift characters char shift$\_$char$($char c$,$ int shift$)\{$ if $($c $>=\text{'}$a$\text{'}$ && c $<=\text{'}$z$\text{'})\{$ return $\text{'}$a$\text{'}+((($c $-\text{'}$a$\text{'})+$ shift $+26)\%26)$; $\}$ else if $($c $==\text{'}\text{'})\{$ return $\text{'}$z$\text{'}$; $//$ Encrypt space to $\text{'}$z$\text{'}\}$ return c; $\}//$ Encrypt single char char encrypt$($char c$,$ int shift$)\{$ return shift$\_$char$($tolower$($c$),$ shift$)$; $\}//$ Decrypt single char char decrypt$($char c$,$ int shift$)\{$ return shift$\_$char$($tolower$($c$),-$shift$)$; $\}$ void process$($char mode, int shift, char dir$)\{$ int effective$\_$shift $=($dir $==\text{'}$l$\text{'})?-$shift : shift; std::string phrase; std::cout $<<$ "Enter the phrase to $"<<($mode $==\text{'}$e$\text{'}?$ "encrypt: $"$ : "decrypt: $")$; std::getline$($std::cin, phrase$)$; std::cout $<<$ "Result: $"$; for $($char c : phrase$)\{$ if $($mode $==\text{'}$e$\text{'})\{$ std::cout $<<$ encrypt$($c$,$ effective$\_$shift$)$; $\}$ else $\{$ std::cout $<<$ decrypt$($c$,$ effective$\_$shift$)$; $\}\}$ std::cout $<<$ std::endl; $\}$

main.cpp:

#include #include #include "encrypt.h$"$ using namespace std; $//$ Function declarations char main$\_$menu$()$; void get$\_$opts$($int &shift, char &dir$)$; $//$ Display the main menu and return the selected option char main$\_$menu$()\{$ char choice; do $\{$ std::cout $<<$ "Please select from the following options:

$"$; std::cout $<<$ "Encrypt $($e$)$

Decrypt $($d$)$

Quit $($q$)$

$"$; std::cout $<<$ "Choice: $"$; cin $>>$ choice; if $($choice $!=\text{'}$e$\text{'}$ && choice $!=\text{'}$d$\text{'}$ && choice $!=\text{'}$q$\text{'})\{$ std::cout $<<$ choice $<<"$ is not a valid option, try again.

$"$; $\}\}$ while $($choice $!=\text{'}$e$\text{'}$ && choice $!=\text{'}$d$\text{'}$ && choice $!=\text{'}$q$\text{'})$; return choice; $\}$ void get$\_$opts$($int &shift, char &dir$)\{$ cout $<<$ "Enter the direction of the shift $($l$/$r$)$: $"$; cin $>>$ dir; cout $<<$ "Enter the shift number $($integer$)$: $"$; cin $>>$ shift; std::cin.ignore$($std::numeric$\_$limits::max$(),\text{'}$

$\text{'})$; $//$ Clear the input buffer $\}//$ Main program entry point. int main$()\{$ char choice; do $\{$ choice $=$ main$\_$menu$()$; if $($choice $==\text{'}$e$\text{'}||$ choice $==\text{'}$d$\text{'})\{$ int shift; char dir; get$\_$opts$($shift$,$ dir$)$; process$($choice$,$ shift, dir$)$; $//$ Call process to perform encryption$/$decryption $\}\}$ while $($choice $!=\text{'}$q$\text{'})$; std::cout $<<$ "Goodbye!

$"$; return $0$; $\}$

HOW TO FIX OUTPUT:

TO GET:

Please select from the following options:

Encrypt $($e$)$

Decrypt $($d$)$

Quit $($q$)$

Choice: e

Enter the direction of the shift $($l$/$r$)$: l

Enter the shift number $($integer$)$: $3$

Enter the phrase to encrypt: cats and dogs

Result: yqpxykaxaldp

Please select from the following options:

Encrypt $($e$)$

Decrypt $($d$)$

Quit $($q$)$

Choice: d

Enter the direction of the shift $($l$/$r$)$: l

Enter the shift number $($integer$)$: $3$

Enter the phrase to decrypt: yqpxykaxaldp

Result: cats and dogs