A small application of cash-register

[daisy_polly]

Hi,

I am making a small application of a cash register that add's items,get total amount etc. My add function does not work and neither does the total function. If someone could help me it will be greatly appreciated.

char itemName;
float itemPrice=0;
float total;
int numberOfItems=0;
int number;
char scanItem;
float scanPrice;
void add(float itemPrice,char itemName);
float getTotal();
float calaverage();
int main(int argc, char *argv[]){


while (1) {
    printf("1. Add Item\n");
    printf("2. Compute Total\n");
    printf("3. Compute Average\n");
    printf("4. Compute Change\n");
    printf("5. Reset Cash-register\n");
    printf("6. Quit\n");
    printf("Enter Option: ");
    scanf("%d",&number);

if(number==1){

    scanf("%f,%c",&scanPrice,&scanItem);
    add(scanPrice,scanItem);
    //printf("%4f %c",itemPrice,scanItem);

}

else if(number==2){
float totalPrice = getTotal();
  printf("%f",&totalPrice);

}
else if(number==4){
    printf("you pressed4\n");
}
else if(number==5){
    printf("you pressed5\n");
}
else if(number==6){
    break;
}
else{
     printf("Invalid Option\n");
 }

   }

}

void add(float aPrice,char aName){
    itemPrice = aPrice;
    itemName = aName;
    total=total+aPrice;
    numberOfItems=numberOfItems+1;
}

float getTotal(){
	return total;
}

float calaverage(){ total/numberOfItems;}

[Richie T]

i will assume that you are a beginner by the number of issues
with your code so i'll be gentle. firstly, you didnt include any
header files in the code you supplied, i think that might have
been a cut and paste mistake so we'll let that slide. secondly,
you are breaking a very very very basic program into too many
functions, the only way you have of dealing with it is to use
global variables, which (for one reason or another) is not
considered good practice. you could write code in about 50 lines
to do all of your operations, maybe even less. thirdly, because
each menu choice calls its own function, it would be a good idea
to use switch statements as opposed to if and else statements.
also, you dont need to use braces for these if only one statement
is to be executed by the if/else thingy - as visible in the code
below. finally, you need some style - your naming convention
of variables is a little bit off (first letter uncapitalised, then
the first letter of the next word within the variable name is???).
that alone is forgiveable, but only initialising some of the variables
and using the full definition of main when it is not used, not
returning 0 at the end of the program, inconsistent brace and
text indentations, and also the use of the c++ comment specifier
all need to be addressed, because before you know it, you
get asked to write code on a different setup and low and behold,
you run into a number of errors that you have no idea how to
solve!

here is your code, modified and operational. i used strings to
specify an item name, since your previous code only allowed
for the entry of a single character. all the same, you don't
need the name of your items as your code stood, unless you
wanted to do code to print a receipt, but you really would need
to approach the whole program in a more advanced way - i would
use structs, and probably not break into 5 separate functions,
thus completely avoiding need for global variables.

i dont want to appear harsh, but you needed to know these
things. my solution here is not the best possible, there are ways
that this approach could be improved, but i didnt bother as the
real way i would approach this is as said before, with a struct.

#include <stdio.h>		/*Needed Header*/
#include <string.h>     /*to use string functions*/

char itemName [50];
float itemPrice = 0;
float total = 0;  /*This needed to be initialised definitely*/
int numberOfItems = 0;
int number = 0;
char scanItem [50];
float scanPrice = 0;

void add(float aPrice, char aName [50]);

float getTotal();

float calaverage();

int main(void){

/*also just want to point out that spacing your
code appropraitely will make it much more readable*/

while (1) {
    printf("1. Add Item\n");
    printf("2. Compute Total\n");
    printf("3. Compute Average\n");
    printf("4. Compute Change\n");
    printf("5. Reset Cash-register\n");
    printf("6. Quit\n");
    printf("Enter Option: ");
    scanf("%d",&number);

    if(number==1){
	printf ("\nEnter Price: ");
	scanf("%f",&scanPrice);
	printf ("Enter item name: ");
	scanf ("%s", scanItem);
	printf ("\n");
	add(scanPrice,scanItem);
	}

    else if (number == 2)
	printf ("Total is %f\n\n", getTotal());

    else if (number == 3)
	 printf ("The average is %f\n\n", calaverage ());

    else if (number == 6)
	break;
  
    else
	printf("Invalid Option\n");
}
return 0;
}



void add(float aPrice,char aName [50]){
    itemPrice = aPrice;
    strcpy (itemName, aName);
    total=total+aPrice;
    numberOfItems++;
}

float getTotal(){
    return total;	/*i mean there is no justification for a function like this*/
}

float calaverage(){
    return total/numberOfItems; /*or this*/
}

[spydoor]

you are breaking a very very very basic program into too many
functions, the only way you have of dealing with it is to use
global variables

Having many functions has nothing to do with needing global variables, and generally it is a good thing to separate logic into functions. I do agree that a function that just returns a global variable is completely pointless.

you dont need to use braces for these if only one statement
is to be executed by the if/else thingy

This is a matter of style and neither way is better than the other. Often it is helpful for new programmers to include braces around all block statments, even one-liners. At the very least it may prevent bugs when additional logic is added, and some find it more readable (myself included).

The code posted in the second example is formatted better, but I don't think most would consider it correct.

[Richie T]

perhaps i was unclear in my statement in global variables, the
only way that newbie have of dealling with a number of functions
that must access the same data is most often through global
variables. also regarding functions, i do think that it is more
than possible to break a program into too many functions, as it
can confuse issues for inexperienced programmers - the add
function would be the only code that i would even consider
creating a function for myself, but fair point, that is a matter for
structure and doesnt have much of a detrimental effect. with
respect to the solution i proposed, it is most definitely not the
best way to do it but i wanted to keep the code as similar to
the authors original work so they can make comparisons and see
how it works, and also to extend on it more easily. hope this
clarifies my standpoint.

[ssharish2005]

well, i seems that your add fucntion works fine for me and gives the reults of what u expect. and Richie has some good points for u. and if u could explain a bit more about u'r ptoblem. probabaly could help us work through it better way.

ssharish2005

[kumar14878]

You can handle these type of problems with switch and case commands, it is always easy to handle the optional programmes using switch and case statements.

switch(input)
{
case <option>:
statement
.
.
.
.
default :
statement
.
.
}

[daisy_polly]

thanks for a lot of helpful suggestion. I have one more question.
How do I display all the entries that have been added.

thanks

[Richie T]

there lies a problem. the way you have set up individual variables
means that if a user enters a number of items, only the last
entered one is saved - previous ones get overwritten. This is
why structs are the way to go for this application as i mentioned
before, as the allow you to group all of the data relevant to a
specific item, namely the price and the name. however since
you have suggested that you are a beginner, this is probably
going to be a bit difficult to get your head around.

http://www.cprogramming.com/tutorial/c/lesson7.html

what you are looking for is an array of structs, each element
of this array would then be capable of storing the item name and
its price. that should point you in the right direction

[kumar14878]

Hi daisy_polly,
Your most welcome.
To display all the enteries entered by you, you need to store all the records in a seperate data file, for that u need to use file stream and then you can only retrieve all the records and display.


Thanx