/**
- struct instruction_s - opcode and its function
- @opcode: the opcode
- @f: function to handle the opcode
- Description: opcode and its function
- for stack, queues, LIFO, FIFO
- struct instruction_s - opcode and its function
- @opcode: the opcode
- @f: function to handle the opcode
- Description: opcode and its function
- for stack, queues, LIFO, FIFO **/