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What is symbol table?

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Satyamevjayte Haxor

The document summarizes a seminar presentation on symbol table generation. It defines what a symbol table is, explaining that it collects information about identifiers in a source program like their storage allocation, type, and scope. This information includes the type of arguments for procedures, how arguments are passed, and the return type. A symbol table is necessary because declarations appear once but uses may be in many places, and it is used by compiler phases for type checking, verifying definitions are used correctly, and generating code.

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Walchand Institute of Technology Seminar On Symbol Table Genearation Presented by…… Name Shikha Gajul Pooja Kingi Kavita NamaBabita Pobatti Vaishali
What is Symbol Table ? The compiler has to identifier used in source program. It has to collect information about them like storage allocation for an identifier it’s type, scope where in program they are valid and in procedure name information about the : Type of its argument, Method of passing of this arguments , Type returned. All this is stored in data structure called Symbol Table. A symbol table is a necessary component because  Declaration of identifiers appears once in a program  Use of identifiers may appear in many places of the program text
USE OF SYMBOL TABLE Symbol table information is used by the analysis and synthesis phases. To verify that used identifiers have been defined (declared). To verify that expressions and assignments are semantically correct – type checking. To generate intermediate or target code.
#include<stdio.h> #include<conio.h> #include<string.h> void check_var(); FILE *fp; char ch; int i,j,k,m,ptr; char *str1[]={"int","float","char"}; void main() { char *word; clrscr(); printf("ntData type tLengthttSymbolttAddress"); fp=fopen("c:turboc3s.c","r"); if(fp==NULL) { printf("nCan't open a file."); return; }
while((ch=fgetc(fp))!=EOF) { i=0; *word=NULL; while((ch!='n')&(ch!=' ')&(ch!=EOF)) { word[i]=ch; ch=fgetc(fp); i++; } m=strlen(word); if(m!=i) { word[i]='0'; } for(k=0;k<3;k++) { ptr=strcmp(&(str1[k][0]),word); if(ptr==0) check_var(word); } } getch(); }
void check_var(char *word) { char word1[10]; int n; ch=fgetc(fp); while((ch!=';')&&(ch!='n')&&(ch!=EOF)) { printf("nnt"); fputs(word,stdout); if(k==0) fputs("tt2 bytes",stdout); else if(k==1) fputs("tt4 bytes",stdout); else if(k==2) fputs("tt1 byte ",stdout); n=0;
while((ch!=',')&&(ch!=';')&&(ch!=EOF)) { word1[n]=ch; ch=fgetc(fp); n++; } m=strlen(word1); if(m!=n) { word1[n]='0'; } printf("tt%s",word1); printf("tt%ld",*word1); ch=fgetc(fp); } return; }
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What is symbol table?

  • 1. Walchand Institute of Technology Seminar On Symbol Table Genearation Presented by…… Name Shikha Gajul Pooja Kingi Kavita NamaBabita Pobatti Vaishali
  • 2. What is Symbol Table ? The compiler has to identifier used in source program. It has to collect information about them like storage allocation for an identifier it’s type, scope where in program they are valid and in procedure name information about the : Type of its argument, Method of passing of this arguments , Type returned. All this is stored in data structure called Symbol Table. A symbol table is a necessary component because  Declaration of identifiers appears once in a program  Use of identifiers may appear in many places of the program text
  • 3. USE OF SYMBOL TABLE Symbol table information is used by the analysis and synthesis phases. To verify that used identifiers have been defined (declared). To verify that expressions and assignments are semantically correct – type checking. To generate intermediate or target code.
  • 4. #include<stdio.h> #include<conio.h> #include<string.h> void check_var(); FILE *fp; char ch; int i,j,k,m,ptr; char *str1[]={"int","float","char"}; void main() { char *word; clrscr(); printf("ntData type tLengthttSymbolttAddress"); fp=fopen("c:turboc3s.c","r"); if(fp==NULL) { printf("nCan't open a file."); return; }
  • 5. while((ch=fgetc(fp))!=EOF) { i=0; *word=NULL; while((ch!='n')&(ch!=' ')&(ch!=EOF)) { word[i]=ch; ch=fgetc(fp); i++; } m=strlen(word); if(m!=i) { word[i]='0'; } for(k=0;k<3;k++) { ptr=strcmp(&(str1[k][0]),word); if(ptr==0) check_var(word); } } getch(); }
  • 6. void check_var(char *word) { char word1[10]; int n; ch=fgetc(fp); while((ch!=';')&&(ch!='n')&&(ch!=EOF)) { printf("nnt"); fputs(word,stdout); if(k==0) fputs("tt2 bytes",stdout); else if(k==1) fputs("tt4 bytes",stdout); else if(k==2) fputs("tt1 byte ",stdout); n=0;
  • 7. while((ch!=',')&&(ch!=';')&&(ch!=EOF)) { word1[n]=ch; ch=fgetc(fp); n++; } m=strlen(word1); if(m!=n) { word1[n]='0'; } printf("tt%s",word1); printf("tt%ld",*word1); ch=fgetc(fp); } return; }