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Program Control Instructions  • Branch Instructions  • Procedure Call and Return Instructions A program control instruction changes address value in the PC and hence the normal flow of execution.  • Change in PC causes a break in the execution of instructions.  • It is an important feature of the computers since it provides the control over the flow of the program and provides the capability to branch to different program segments. Typical Program Control Instructions  • Branch (BR) and Jump (JMP) instructions are used sometimes interchangeably but, they are different.  • Branch and Jump instructions usually differ in addressing modes. • Usually Jump is used to refer to unconditional version of branch.  • Skip (SKP) instructions is used to skip one(next) instruction. It can be conditional or unconditional. It does not need an address field.  • In case of conditional skip instruction, the combination of conditional skip and a unconditional branch can be used an alternative

Types of Instructions: mostly classified into 3 types Data Transfer Instructions : Data Manipulation Instructions Program Control Instructions Data Transfer Instructions : Data transfer instructions cause transfer of data from one location to another without changing the information content. load,store,move, input,out put, push,pop are data transfer instructions. The common transfers may be between memory and processor registers, between processor registers and input/output. The stack instructions push and pop transfer data between a memory stack and a processor register or memory. The push operation places an item onto the top of the stack (TOS).  • The pop operation removes one item from the TOS.  • Stack is basically part of the memory, and to provide the logic of pushing and popping a register is used which is called Stack Pointer (SP). Independent(Isolated) vs Memory-Mapped I/O  There are two techniques for address I/O devices by CPU Memory mapped I

Computer Organization | Stack based CPU Organization STACK ORGANIZATION .  Stack  is a storage structure that stores information in such a way that the last item stored is the first item retrieved. It is based on the principle of LIFO (Last-in-first-out). The  stack in digital computers is a group of memory locations with a register that holds the address of top of element. The computers which use Stack-based CPU Organization are based on a data structure called  stack . The stack is a list of data words. It uses  Last In First Out (LIFO)  access method which is the most popular access method in most of the CPU. A register is used to store the address of the topmost element of the stack which is known as  Stack pointer (SP) . In this organisation, ALU operations are performed on stack data. It means both the operands are always required on the stack. After manipulation, the result is placed in the stack. The main two operations that are performed on the operators of

Components of CPU and their functions: CPU or  Central processing unit  is the brain of the computer system. Functions of CPU varies from data processing to controlling input-output devices. Each and every instruction no matter how complex or simple, it has to go through the CPU. In this article we will learn various components of CPU and their functions. So, let us say we press a key on the keyboard and it instantly appears on our computer monitor so the CPU of the computer is what makes this possible. The central processing unit is also responsible for storing data or information, intermediate results and instructions in the memory system. It also controls the operations of all other parts of the computer system. Functions of a CPU: CPU generally performs the arithmetical and logical operations, controlling of different input-output devices. These operations are performed based on some predefined algorithms and ins