Arrays and Functions in c - c

Question

I am just starting to work with functions and wish to read an entire array of user input and convert all entries to uppercase. I am still a little confused how to change things in functions and have the changes occur in the array in the main program.
The code I attached is not working:
Any help and/or explanation would be appreciated.
Thank you
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <ctype.h>
// function to turn all user input to uppercase
turnUpCase(char *in,200)
{
char *p;
for (p=in; *p='\0'; ++p)
{
*p = toupper(*p);
}
}
int main(void)
{
char input[200];
int i = 0;
printf("Welcome to the Morse translator.\n");
printf("Enter input: ");
fgets(input, sizeof(input), stdin);
// call to function to turn all input into uppercase
turnUpCase(&input);
return 0;
}

Answer 1

For your turnUpCase function:
1- You are not mentioning any return type.
2- what is 200 ?? write it as retyrn_type turnUpCase(char *p, int size)
in for loop write it as
for (p=in; *p!='\0'; ++p) //to compare with anything use '=='
Name of array is always a pointer. You don't need to mention like turnUpCase(&input). let it go like turnUpCase(input,200)

Answer 2

modify:
turnUpCase(&input); //turnUpCase(input)
turnUpCase(char *in,200) //turnUpCase(char *in)
*p='\0' // *p!='\0'

Answer 3

To make your code work, first you need to change the declaration for turnUpCase() to something like:
void turnUpCase(char *in){}
Since your function does not return a value, it should be declared to be of type void. Next, in the for-loop of the function itself, you have an assignment instead of a comparison. Try this:
for (p = in; *p != '\0'; ++p){}
Finally, when you pass an array to a c function, you are really passing a pointer to the first element of the array, so in your case turnUpCase(input) passes a pointer to the first character of the input string to your function. The way you wrote it, you are passing the address of a pointer to the first character.
Incidentally, I might have written your function like this:
void to_upper(char *str)
{
while(*str) {
*str = toupper(*str);
++str;
}
}

Answer 4

change turnUpCase(&input); to turnUpCase(input); ( an array if passed to a function, "decays" to a pointer to its 1st element, so you don't need to use &) and
also:turnUpCase(char *in,200) to void turnUpCase(char *in) and *p='\0' to *p!='\0'.`

Answer 5

I didn't check if there are the proper libraries for this code to run, but the corrected code seems to be:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <ctype.h>
First, we need to declare the method. C needs it inside the header or before the function. Be aware of that this declaration has no body, and ends with ;. After that, we can define the function.
// function to turn all user input to uppercase
void turnUpCase(char *in);
every function needs a return type defined before the definition. Here's the definition and body of the function:
void turnUpCase(char *in) {
char *p;
for (p=in; *p; p++) *p = toupper(*p);
}
Note: As #DavidBowling suggested, this code can be rewritten as (I prefer keeping the original pointer as it was) :
void turnUpCase(char *in) {
char *p = in;
while(*p){
*p = toupper(*p);
p++;
}
}
Both methods check the chars until it reaches a zero char/string end char/null char. Every string in C ends with an \0 (0x00) character, so the function tells that until our string ends, loop the chars and make every char uppercase.
Now the magic begins:
int main(void) {
char input[200];
int i = 0;
printf("Welcome to the Morse translator.\n");
printf("Enter input: ");
fgets(input, sizeof(input), stdin);
Here, you don't need the addressing & operator, because in C, char arrays are already a pointer to it's contents. But, you might give the first char's address to the method too. So there are two options.
First:
// call to function to turn all input into uppercase
turnUpCase(input);
Second:
// call to function to turn all input into uppercase
turnUpCase(&input[0]);
Then, you can print the result to user.
printf("The uppercase version is: %s", input);
return 0;
}

Answer 6

i compile your code with c++ 4.2.1, and it seems has some compilation error.
when you claim a string, input variable is the pointer of first char in string, so it should be turnUpCase(input) when you call the function.
if want to change variable in function, you need to pass pointer or reference into it. in this case, pass input is just fine.
the reason your code not work may be:
for (p=in; *p='\0'; ++p)
should be:
for (p=in; *p=='\0'; ++p)