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cscan.c
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cscan.c
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/*
C-SCAN: Circular Scan
- Scans towards the nearest end and works it way all the way to the end of the system.
- Once it hits the bottom or top it jumps to the other end and moves in the same direction.
*/
#include <stdlib.h>
#include <stdio.h>
#define HIGH 199
#define LOW 0
int main(){
int queue[20], q_size, head, i,j, seek=0, diff, max, temp, queue1[20], queue2[20], temp1=0, temp2=0;
float avg;
printf("%s\t", "Input no of disk locations");
scanf("%d", &q_size);
printf("%s\t", "Enter initial head position");
scanf("%d", &head);
printf("%s\n","Enter disk positions to be read");
for(i=0; i<q_size; i++) {
scanf("%d", &temp);
if(temp >= head){
queue1[temp1] = temp;
temp1++;
} else {
queue2[temp2] = temp;
temp2++;
}
}
//sort both arrays
for(i=0; i<temp1-1; i++){
for(j=i+1; j<temp1; j++){
if(queue1[i] > queue1[j]){
temp = queue1[i];
queue1[i] = queue1[j];
queue1[j] = temp;
}
}
}
for(i=0; i<temp2-1; i++){
for(j=i+1; j<temp2; j++){
if(queue2[i]>queue2[j]){
temp = queue2[i];
queue2[i] = queue2[j];
queue2[j] = temp;
}
}
}
//calculate closest edge
if(abs(head-LOW) >= abs(head-HIGH)){
for(i=1,j=0; j<temp1; i++,j++){
queue[i] = queue1[j];
}
queue[i] = HIGH;
queue[i+1] = 0;
for(i=temp1+3, j=0; j<temp2; i++, j++){
queue[i] = queue2[j];
}
} else {
for(i=1,j=temp2-1; j>=0; i++,j--){
queue[i] = queue2[j];
}
queue[i] = LOW;
queue[i+1] = HIGH;
for(i=temp2+3, j=temp1-1; j>=0; i++, j--){
queue[i] = queue1[j];
}
}
queue[0] = head;
for(j=0; j<=q_size+1; j++){
diff=abs(queue[j+1] - queue[j]);
seek += diff;
printf("Disk head moves from %d to %d with seek %d\n",queue[j],queue[j+1],diff);
}
//seek = seek - max; //subtract seek time back to zero
printf("Total seek time is %d\n", seek);
avg = seek/(float)q_size;
printf("Average seek time is %f\n", avg);
return 0;
}