Two-pass-Assembler

Designed a 32-bit ISA and implemented a two pass assembler using C code to demonstrate how assembly language computation occurs with the help of different sets of instructions and different addressing modes defined in ISA. It converted Assembly Language code into Machine Language code and then using the machine language code generated executed the program.

#MANUAL TO USE THE ISA -AYUSH PAREEK THE PROGRAMS PROGRAM 1 :: Find frequency of a given number in an integer array PROGRAM 2 :: Binary Search for an integer

PART 1 :: FROM ASSEMBLY CODE TO BINARY How to use ? =>Extract everything to the single folder =>Put the assembly code in ‘input_instructions.txt’ =>Run main and give the base address as 200 (or any value much lesser than 1024) =>Output machine code is found in ‘output_machine_code.txt’ NOTE :: Pre-run inputs and outputs can be found ‘Assembly CODE 1’(‘Assembly CODE 2’) and ‘Output Code1’(‘Output Code2’) Abstract Explanation of Algorithm STEP1:: Opcodes along with their assigned machine codes and expected operand formats i.e. /** rri = reg reg imm. addr. rrr = reg reg reg ri = reg imm. rr = reg reg a = add z = zero */

are read from ‘input_opcode.txt’ by the program and are stored as a HASH TABLE( to reduce time complexity while searching for those opcodes) /We have used 2 pass assembler to remove forward addressing problem/ STEP2:: In pass 1, a symbol table of all labels is generated which can be read in ‘symbol_table.txt’ STEP3::In pass 2, the program in again read and symbol table is used to get the corresponding addresses associated with each label. Each instruction is converted to 32 bit machine code Addressed associated with registers R0-----> 00000 R1-----> 00001 R2-----> 00010 R3-----> 00011 R4-----> 00100 R5-----> 00101 R6-----> 00110 R7-----> 00111 R8-----> 01000 R9-----> 01001 R10-----> 01010 R11-----> 01011 R12-----> 01100 R13-----> 01101 R14-----> 01110 R15-----> 01111 /SPECIAL ARRAY REGISTERS FOR STORING THE SIZE OF THE ARRAY/ A0-----> 10000 A1-----> 10001 A2-----> 10010 A3-----> 10011 PART 2 :: FROM BINARY CODE TO EXECUTION How to use ? (similar to previous file) /Use testbit.c with gcc -lm/ Abstract Explanation of Algorithm We are storing the opcodes in a Binary Trie . Thus we have refrained from storing the machine codes corresponding to opcodes in additional space. This data structure saves huge amount of memory since no machine code is actually being stored.

The searching also takes place using this trie. Thus, we have implemented the most optimized scheme of Using trie, search complexities can be brought to most optimal limit (opcode length). This guarantees search in O(p) time where p is the length of the largest opcode. This scheme is much better than trial and error using masking in both time and space complexities.

The opcodes corresponding to the machine instruction is extracted and executed.