LEXICAL ANALYSER

#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>
main()
{
char buff[30],c,ch;
char key[5][10]={"int\0","char\0","float\0","main\0"};
FILE *fp;
int i,j,k,l,m;
clrscr();
fp=fopen("add.c","r");
while(1)
{
ch=fgetc(fp);
c=ch;
if(c==EOF)
break;
if(c=='+'||c=='-'||c=='*'||c=='/')
{
buff[0]=c;
c=fgetc(fp);
if(c=='+'||c=='-'||c=='=')
printf ("%c%c\t is operator\n",buff[0],c);
else
{
printf("%c is operator\n",buff[0]);
fseek(fp,0,-1);
}
}
else if(c=='=')
{
buff[0]=c;
c=fgetc(fp);
if(c=='=')
printf("%c%c\t is comparision\n",buff[0],c);
else
{
printf("%c is assignment\n",buff[0]);
fseek(fp,0,-1);
}
}
else if(isdigit(c))
{
i=0;
buff[i]=c;
c=fgetc(fp);
while (isdigit(c))
{
i++;
buff[i]=c;
c=fgetc(fp);
}
for(k=0;k<=i;k++)
{
printf("%c",buff[k]);
}
printf("\t is number\n");
fseek(fp,0,-1);
}
else if(isalnum(c))
{
m=0;
i=0;
do
{
buff[i]=c;
c=fgetc(fp);
i++;
}while(isalnum(c));
buff[i]='\0';
for(j=0;j<4;j++)
{
if(strcmp(buff,key[j])==0)
{
m=1;
printf(" %s is key word\n",buff);
break;
}
}
if(strcmp(buff,key[j])!=0)
{
printf(" %s is a identifier\n",buff);
}
fseek(fp,0,-1);
}
}
fclose(fp);
getch();
}

RECURSIVE PARSING

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
char input[10];
int i=0;
void t();
void eprime();
void f();
void tprime();
void e()
{
if(input[i+1]=='+')
eprime();
else if(input[i+1]=='*')
{
t();
e();
}
else if(input[i]=='\0')
printf("string not accepted");

else
{
f();
e();
}
}
void t()
{
if(input[i+1]=='*')
tprime();
else if(input[i]=='\0')
printf("string not accepted");
else
f();
}
void f()
{
if(input[i]=='(')
{
i++;
e();
}
else if(input[i]==')' && input[i+1]=='\0')
printf("string is accepted");
else if(input[i]=='I')
{
i++;
if(input[i]=='\0'||input[i]==')')
{
printf("string is accepted");
exit(0);
}
}
}
void eprime()
{
f();
i++;
e();
}
void tprime()
{
f();
i++;
e();
}
main()
{
clrscr();
printf("enter the string replacing id with I\n");
scanf(" %s",input);
e();
getch();
}

3ADDRESS CODE

#include<stdio.h>
#include<ctype.h>
main()
{
char expr[20],stack[20];
int i,top=0,k=0,num[20];
printf("enter the postfix expression\n");
scanf("%s",&expr);
for(i=0;expr[i]!='\0';i++)
if(isalnum(expr[i]))
stack[top++]=expr[i];
else
{
printf("T%d=",k);
if(stack[top-2]=='T')
printf("%c%d",stack[top-2],num[top-2]);
else
printf("%c",stack[top-2]);
printf("%c",expr[i]);
if(stack[top-1]=='T')
printf("%c%d",stack[top-1],num[top-1]);
else
printf("%c",stack[top-1]);
printf("\n");
top=top-2;
stack[top]='T';
num[top++]=k++;
}
}

CYCLIC REDUNDANCY CHECK PROGRAM

#include<iostream.h>
#include<conio.h>
#include<stdio.h>
int main() //int avgc,char *avgv[];
{
int val1[20],val2[20],val3[20],val4[20];
int x,i,j,n,m,a,s;
clrscr();
cout<<"enter no .of generating fu.bits";
cin>>n;
cout<<"\n";
cout<<" enter gen.fu";
cout<<"\n ";
for (i=0;i<n;i++)
{
cin>>val1[i];
}
cout<<"gen.fu";
cout<<"\n";
for(i=0;i<n;i++)
{
cout<<val1[i];
}
cout<<"\n";
cout<<" enter no .of bits of polynomial";
cout<<"\n";
cin>>n;
cout<<"enter polynomial ";
cout<<"\n";
for(i=0;i<m;i++)
{
cin>>val2[i];
val4[i]=val2[i];
}
cout<<"\n";
cout<<" polynomial";
cout<<"n";
for(i=0;i<m;i++)
{
cout<<val2[i];
}
cout<<"\n";
cout<<"\n";
for(i=m;i<m+n-1;i++)
{
val2[i]=0;
}
cout<<"\n";
cout<<"appened polynomial i";
for(i=0;i<m+n-1;i++)
{
cout<<val2[i];
}
a=m+(n-1);
for(i=0;i<m;i++)
{
if(val2[i]==0)
{
for(i=1;j<n+i;++j)
val2[j]=val2[j]^0;
}
else
{
val2[i]=val2[i]^val2[0];
val2[i+1]=val2[i+1]^val1[1];
val2[i+2]=val2[i+2]^val1[2];
val2[i+3]=val2[i+3]   ^val1[3];
}
}
cout<<"\n \t the crc is !";
for(i=m;i<a;++i)
cout<<val2[i];
for(i=m,j=m;j<a,i<m+n-1;j++,i++)
{
val4[i]=val2[j];
}
cout<<"crc matrix is :";
cout<<"\n";
for(i=0;i<m;i++)
{
if(val4[i]==0)
{
for(j=i;j<n+i;++j)
val4[j]=val4[i]^val1[0];
val4[i+1]=val4[i+1]^val1[1];
val4[i+2]=val4[i+2]^val1[2];
val4[i+3]=val4[i+3]^ val1[3];
}
}
cout<<"\n\t after error check is :";
for(i=m;i<a;i++)
{
cout<< val4[i];
}
cin>>x;
return 0;
}

CHARACTER STUFFING PROGRAM

#include<stdio.h>
#include<conio.h>
#include<string.h>
void start();
void end(char);
FILE *of;
FILE *cf;
int b,i=0;
char c,a='@',z='$',d[25];
void main()
{
clrscr();
cf=fopen("andy.txt","r");
of=fopen("ani.txt","w");
do
{
c=getc(cf);
d[i++]=c;
}while(c!=EOF);
fprintf(of,"%c",a);
for(i=0;i<strlen(d);i++)
{
if(d[i]==' '||d[i]=='\t')
{
end(d[i]);
}
else if(d[i]=='\n')
{
start();
}
else if(d[i]==EOF)
{
fprintf(of,"%c",z);
}
else
{
fprintf(of,"%c",d[i]);
}
}
printf("file sucessfully stuffed");
fclose(cf);
fclose(of);
getch();
}
void start()
{
fprintf(of,"%c\n",z);
fprintf(of,"%c",a);
}
void end(char k)
{
fprintf(of,"%c",z);
fprintf(of,"%c",a);
fprintf(of,"%c",k);
fprintf(of,"%c",z);
fprintf(of,"%c",a);
}

ROUND ROBIN

#include<stdio.h>
#include<conio.h>
void main()
{
int n,i,t=0,s=1;
int a,q,x,*b;
clrscr();
printf("enter number of processes");
scanf("%d",&n);
for(i=1;i<=n;i++)
{
printf("process %d",i);
scanf("%d",&b[i]);
}
printf("enter time quantum");
scanf("%d",&q);
x=0;
for(i=1;i<=n;i++)
  t=t+b[i];
printf("total time is = %d\n",t);
for(i=0;i<=n;i++)
{
for(a=1;a<=n;a++)
{
if(b[a]>0)
{
if(b[a]<q && b[a]>0)
   x=x+b[a];
else
   x=x+q;
printf("current program is p %d...%d \n",a,x);
b[a]=b[a]-q;
s++;
}
}
}
getch();
}

PRIORITY SCHEDULING PROGRAM

#include<stdio.h>
#include<conio.h>
void main()
{
int i,j,n,r,s,t,x,d=0,p[20],b[20],pr[20];
clrscr();
printf("enter the no. of process");
scanf("%d",&n);
for(i=1;i<=n;i++)
{
printf("enter burst time %d:",i);
scanf("%d",b[i]);
}
for(i=1;i<=n;i++)
{
printf("priority %d",i);
scanf("%d",pr[i]);
}
for(i=1;i<=n;i++)
{
for(j=i+1;j<=n;j++)
{
if(pr[i]>pr[j])
{
r=p[j];
s=b[j];
t=pr[j];
p[j]=p[i];
b[j]=b[i];
pr[j]=pr[i];
p[i]=r;
b[i]=s;
pr[i]=t;
}
}
}
for(i=1;i<=n;i++)
{
x=x+b[i];
printf("process %d interval is from %d to %d",p[i],d,x);
d=x;
}
getch();
}