Thread: total newbie

hii.

Im afraid im a total newbie to programming and have a code to complete for an assignment but im stuck. the code is meant to pipe in data from a USB using cmd prompt which i have completed.

what i want is to happen is that insted of reading out line 1 and line 2 then line 3 and line 4 then line 5 and line 6 and so on. i want it to read in line 1 and line 2 then line 3 and line 2 again making line 2 dprev and pprev insted of d and p for the second calculation.


where am i going wrong????

Code:

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


int main()


{
    float p, pprev, e;
    int   d, dprev ;




    while (feof(stdin)==0)


       {


        scanf("%d %f", &dprev, &pprev );
        printf(" dprev = %d, pprev = %f\n", dprev,pprev);




        scanf("%d %f", &d, &p );
        printf("d = %d,p = %f\n", d, p);


        e = 100 * pprev / (d - dprev);


        printf("The efficiency is %f\n", e);




        dprev = d;
        pprev = p;


      }
        return 0;
    }

my data is
54752 2.64
53247 2.87
52247 2.20
57412 2.78
59321 2.58
49665 2.86
52001 2.55

Thanks

Or does this even make since :P

Thanks for the reply.

I do want it to read in the values from the two lines in one loop. i want it to read d prev as 54752 and pprev as 2.64 and d 53247 as and p as 2.87 in the first loop and then 53247 will be dprev and 2.87 will be pprev and i will take 52247 and 2.20 as d and p in the second loop if that makes since

There are a few ways you can go about this.

One would be to, before the loop, read the initial values into "dprev" and "pprev". Then you enter the loop, reading into "d" and "p", do your calculations (or whatever), and then move "d" into "dprev" and "p" into "pprev", and repeat.

Is that along the lines of what you were thinking?

Originally Posted by Matticus

There are a few ways you can go about this.

One would be to, before the loop, read the initial values into "dprev" and "pprev". Then you enter the loop, reading into "d" and "p", do your calculations (or whatever), and then move "d" into "dprev" and "p" into "pprev", and repeat.

Is that along the lines of what you were thinking?

Yea exactly.

I want to use the previous d and p as the dprev and prev in the next loop

Originally Posted by stephen8ofclubs

Yea exactly.

I want to use the previous d and p as the dprev and prev in the next loop

[Apologies to anduril462 - I just realized my suggestion simply echoed his.]

So you've been given an approach to consider - have you tried coding it yet?

thanks for that

so should my while loop look like

Code:

 while ( scanf("%d %f", &dprev, &pprev == 2 ))

???

Originally Posted by stephen8ofclubs

thanks for that

so should my while loop look like

Code:

 while ( scanf("%d %f", &dprev, &pprev == 2 ))

???

Um no, as

Code:

while ( scanf("%d %f", &dprev, &pprev) == 2 )

You have a parenthesis in the wrong place (compare your code with the sample given in post #3).

Code:

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


int main()


{
    float p, pprev, e;
    int   d, dprev ;


    scanf("%d %f", &dprev, &pprev );
    printf(" dprev = %d, pprev = %f\n", dprev,pprev);












         while ( scanf("%d %f", &dprev, &pprev) == 2 )
    {


        scanf("%d %f", &d, &p );
        printf("d = %d,p = %f\n", d, p);


        e = 100 * pprev / (d - dprev);


        printf("The efficiency is %f\n", e);




        pprev = p;
        dprev = d;


    }








    return 0;
}

my code now looks like this but when i run it it skips a every second line of the txt. file and so is incorrect calculations ........

Code:

#include <stdio.h>
#include <stdlib.h>
 
 
int main()
 
 
{
    float p, pprev, e;
    int   d, dprev ;
 
 
    scanf("%d %f", &dprev, &pprev );
    printf(" dprev = %d, pprev = %f\n", dprev,pprev);
 
 
 
 
 
 
 
 
 
 
 
 
         while ( scanf("%d %f", &dprev, &pprev) == 2 )
    {
 
 
        scanf("%d %f", &d, &p );
  printf("dprev=%d,pprev=%f\n",dprev,prev); /* this is the important line, you were not printing dprev and pprev */
        printf("d = %d,p = %f\n", d, p);
 
 
        e = 100 * pprev / (d - dprev);
 
 
        printf("The efficiency is %f\n", e);
 
 
 
 
        pprev = p;
        dprev = d;
 
 
    }
  
 
 
    return 0;
}

Look at the line I added, you were not printing dprev and pprev.

and if everything else was same the efficiency value should be correctly calculated even without that printf.

If the data isnt being printed it doesent necessarily mean it isnt being used in the computation.

thanks guys finally think i have i correct.


couldn't have done it without you all.


HAVE A GOOD ONE!!!!