incompatible types in assignment

following is main function of my program

Code:

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#include<stdio.h>
#include"header.h"

main()
{
    unsigned char crc;
    unsigned char ar;
    pdt pv;
    adt av;
    frame *f1;
    frame fr;
   
    int src1=0;
    int dest1=1;

    av.ack=9;
   
//opens a file and assigns a file descriptive to fp
    fp=fopen("txtfile","r");

  //generates stuffed information
  stuff(&pv,fp);
 
    //creates the control byte
    control_byte(&pv);

    //crc is generated for the information
    crc=crc_gent(&pv);

    //frame is created..
    f1=(frame *)make_frame(&pv,crc,src1,dest1);
   
    //push that frame into a buffer
    push(f1);
   
//check for the acknowledgement from the receiver side
    ar=ack_check(&av);

//sliding window is created...
    fr = slide(512,ar); //incompatibe type in assignment
}

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my header file is

Code:

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#include<stdio.h>
//typedef int frame_type;

FILE * fp;

typedef struct payload {
        int frm_typ;
        unsigned char cb;
        unsigned char stuf_info[5];
}pdt;

typedef struct frame {
        char st_flag;
        int src_addr;
        int dest_addr;
        pdt p;
        unsigned char crc;
        char end_flag;
}frame;
struct frame f4[512];

typedef struct ack_frme
{
char st_flg;
int src_addr;
int dest_addr;
unsigned char ack;
char end_flg;
}adt;

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i have problem in
fr = slide(512, ar);


slide function is returning a frame..
but for that line its giving error as incompatible types in assignment.

So where is the prototype for slide() in all of that.

The make_frame() cast is almost certainly wrong for the same reason, except all that you've managed to do is stop the compiler from complaining about it.

thats my main header file.... for each function one library is created and also a header file. in that the function prototypes are declared....

If slide() is defined in slide.c and prototyped in slide.h, then you also need
#include "slide.h"
in your main

This is my slide function... i have taken 'f' as a variable of frame type. and slide function is returning this 'f' which is of frame type.... so in the main function also im receiving this in a variable which is also of type frame... so also it is giving error... im actually not understanding any thing why its giving error????

Code:

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#include<stdio.h>
 #include"header.h"

  int sequence(unsigned char seq);


frame slide(int size,unsigned char seq)    //for sliding window of size 5
 {
    int frameN;
    frame f;
    static int i=-1,j=-1,c=0;          /* i indicates the index of start of window and j indicates the index of last frame sent in the window, required the values of i and j to be static as to persist in the next function calls*/
            int k;                                //index of the frame to sent is remembered in k
    frameN=sequence(seq);
    if(c==5 && frameN==0)                            /* if no acknowledgement is received when window size is over then setting the values of i and j to                                                        retransmit frames*/
    {
      j=i;
      c=0;                                  //resetting window size counter to zero
    }
  else                 
      if(frameN==0)                      // if window counter is less than 5,and acknowledgement is not received then keep on sending frames       
      {
          c++;
          j++;
      }
    else                  //when acknowledgement is received the indices i and j are set according to the sequence no. mentioned in acknowledgement
      {
              i=j=frameN;
          c=0;
      }
        k=j;            // index of the frame to sent is remembered in k
        j++;            //as sendind of frame takes place, index j is increased by one
    f = f4[k];
    return f;
 }

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check your compiler version?

I don't see a prototype of slide() in your header.h file -- and unprototyped functions return int.