Help with program that can respond to user inputs.

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Help with a program that can respond to user inputs.. I'm a beginner in C and would want to know where I am going wrong in regards to syntax and if my conditionals and loops should be changed.
My Skeleton code is as follows;

C++

char *input_strings[] =
{ "Hello", "What is your name?", "How are you?" };
int main(int argc, char **argv)
//infinite loop
	while (1) {
 // get the input string
	printf("> ");
    fgets(input,100,stdin);
     ............ //This is where I created my own code. 
    if (quit_condition) {
 break;

I cannot use any built-in function except StringCMPI which I've done. I would just want clarification on what's wrong.
Thanks.

What I have tried:

C++

#include <stdio.h>
#include <stdlib.h>
char *input_strings[] =
{ "Hello", "What is your name?", "How are you?" };
int main(int argc, char **argv)
char toupp (char ch)
{
	if (ch<=97&&ch<122)
	{
		ch = ch-32;
	}
  return ch;
	}
	int stringCmpi(char*s1,char*s2)
	{
	int i=0, diff =0;
	for(i=0; s1[i]!='\0';i++)
	{
		if (toupp(s1[i]!=toupp(s2[i]))
		{
		return 1;}
		}
		return 0;
		}
{
	char input[100];
 // infinite loop
	while (1) {
 // get the input string
	printf("> ");
	int a = 0, b = 0;
	while (input[a]!='\0'){
	if input (input[a]=='\0''){
		int temp = b +1;
		if (input[temp]!='\0'){
	while(input[temp]=='\0'&&input[temp]!='\0'){
		if input[temp]=='\0'){
			a++;
		}
		temp++;
	    }
		}
		}
		blank[c] = input [b];
		b++
		c++
	}
	if((stringCmpi(input_strings[0],blank))==0)
{
		printf("Hello\n");
}
	else if((stringCmpi(input_strings[1],blank))==0)
{
		printf("My name is NeoNath\n");
}
	else if((stringCmpi(input_strings[2],blank))==0)
  
{		printf("I am fine\n");
  
}
	else if((stringCmpi("BYE",blank))==0)
{
		printf("See you later\n");
break;
}
	else
{
		printf("I do not understand\n");
}
 if (quit_condition) {
 break;
 }
 }
}

Posted 20-Mar-21 9:28am

Member 15084336

Updated 23-Mar-21 1:46am

Patrice T

v2

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Comments

Richard MacCutchan 21-Mar-21 5:46am

	if (ch<=97&&ch<122) // error you mean greater than the first
	{ 
		ch = ch-32;
	}

Don't use numbers to represent characters as they are difficult to understand. Use proper characgter constants:

	if (ch >= 'a' && ch <= 'z') // test for lower case
	{
		ch = ch - 0x040; // show the proper hex value
	}

4 solutions

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OriginalGriff · Answer 1 · 2021-03-20T10:01:00

The C language does not support "nested" functions, so this will not compile:

C++

int main(int argc, char **argv)
char toupp (char ch)
{
	if (ch<=97&&ch<122)
	{

You need to declare the toupp function outside the body of the main function:

C++

char toupp (char ch)
{
	if (ch<=97&&ch<122)
	{
    ...
    }
...
}

int main(int argc, char **argv)
{
...
}

As for the rest of it ... sort your indentation out so it's readable - that's not clear at all!
When you get bits like this:

C++

for(i=0; s1[i]!='\0';i++)
	{
		if (toupp(s1[i]!=toupp(s2[i]))
		{
		return 1;}
		}
		return 0;
		}
{
	char input[100];

It is not at all clear what you meant to have happen!

Rick York · Answer 2 · 2021-03-21T08:30:00

Solution 2

I prefer this function because the logic is a little more clear.

inline int ToUpper( int ch )
{
    const int diff = 'a' - 'A';
    if( ( ch >= 'a' ) && ( ch <= 'z' ) )
        ch -= diff;
    return ch;
}

Posted 21-Mar-21 8:30am

Rick York

Comments

Member 15084336 22-Mar-21 19:33pm

Great, I've used this and have a more updated solution but with a slight isssue.

W∴ Balboos, *GHB* · Answer 3 · 2021-03-23T01:46:00

A nifty way to change case is to use boolean operations. The difference (in ASCII) between UC and LC is a single bit that it toggled. Interestingly that bit is the value of the space character ASCII= 0x100000 (i.e., 32 decimal).

So - you use code like this:

C++

if(isalpha(theChar))
   theChar |= 32;         // sets the bit (to LC)
or
   theChar &= 0x11011111; // clears bit: shown as hex to clarify (to UC)
or
   theChar ^= 32;  // swaps all UC <=> LC

now you have to use home-spun conditionals instead of isalpha() and this have to check the range of theChar to put it between 'a' and 'z', inclusive. I used the isalpha() to give you a bit more real-life with a straight-forward and readable solution that's more flexible.

Member 15084336 · Answer 4 · 2021-03-22T13:32:00

#include <stdio.h>
#include <stdlib.h>

char *input_strings[] = { "Hello", "What is your name?", "How are you?" };
inline int toupper(int ch)
//Upper case converter function.
{
	const int diff = 'a' - 'A';
	if ((ch >= 'a') && (ch <= 'z'))
		ch -= diff;
	return ch;
}

int stringCmpi(char *s1, char *s2)
	{
		int i = 0, diff = 0;
		for (i = 0; s1[i] != '\0'; i++)
		{
			if (toupper(s1[i]) != toupper(s2[i]))
				{
					return 1;
				}
				
		}
				return 0;
	}

			int main(int argc, char **argv)
			{
				char input[100],blank[100];
				// infinite loop
				while (1)
				{
					// get the input string
					printf("> ");
					fgets(input, 100, stdin);
					int a = 0, b = 0;
					while (input[a] != '\0')
					{
						if (input[a] == '\0')
						{
							int temp = a + 1;
							if (input[temp] != '\0')
							{
								while (input[temp] =='\0' && input[temp] != '\0')
								{
									if (input[temp] =='\0')
								{
									a++;
								}

								temp++;
							}
						}
					}

					blank[b] = input[a];
					a++;
					b++;
				}

				blank[b] = '\0';
				//----------------
				//--------------
				if ((stringCmpi(input_strings[0], blank)) == 0)
				{
					printf("Hello\n");
				}
				else if ((stringCmpi(input_strings[1], blank)) == 0)
				{
					printf("My name is JustinNgome\n");
				}
				else if ((stringCmpi(input_strings[2], blank)) == 0)

				{
					printf("I am fine\n");

				}
				else if ((stringCmpi("BYE", blank)) == 0)
				{
					printf("See you later\n");
					break;
				}
				else
				{
					printf("I do not understand\n");
				}
			}

			return 0;

}

Updated Solution; Code runs, yet it's not prompting the user "> " and I will enter a user input such as Hello. 
gcc -o HW3 HW3.c
Instead of receiving > 
I just receive the normal command line of: $ which doesn't take in user inputs such as strings.</stdlib.h></stdio.h>

Help with program that can respond to user inputs.

4 solutions

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