Unit 6: Execution of Program and Programming Languages
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Understanding Program Execution
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Today, we'll start with how a computer executes a program. Can anyone tell me what happens when a program runs on a computer?
It reads the code and runs it, right?
Exactly! It follows a process. This process is called the *instruction cycle*. Do you remember the two main phases of the instruction cycle?
Fetch and execute?
Correct! Remember, 'Fetch' is grabbing the instruction from memory, and 'Execute' performs the instruction. An easy way to remember this is F.E., like the first letters of Fetch and Execute.
Instruction Formats
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Now, let's dive into instruction formats. Each instruction typically contains an opcode and an operand. What do you think is the role of the opcode?
Doesn’t it specify what operation to perform?
Yes! The opcode tells the CPU what to do, while the operand might point to data in memory. An easy mnemonic here is 'O is for Operation', which can help you recall that the opcode describes what operation is needed.
Roles of CPU Registers
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In our discussion of program execution, we must talk about CPU registers like the Program Counter (PC) and the Instruction Register (IR). Can anyone explain the purpose of the Program Counter?
It keeps track of the next instruction to be fetched, right?
Spot on! The PC ensures the CPU knows where to go next. A good way to remember this is 'Program Counter = Next Step Locator'.
Accumulator-based Processors
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Next, let’s discuss how accumulator-based processors work. What do you know about the accumulator?
It stores intermediate results, right?
Absolutely! It’s like a ‘temporary storage’ for results of operations. You can remember this with the phrase, 'Accumulating results'.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section details how programs are executed by processors, elucidating the instruction cycle of fetch and execute phases. It describes different instruction formats, memory operations, the role of CPU registers, and programming languages' hierarchy.
Detailed
Detailed Summary
This section delves into the fundamentals of program execution within computer architecture, detailing how a processor executes a program through a systematic approach involving multiple phases. The instruction cycle is critical to this process, comprising two main phases: Fetch and Execute. The Fetch phase involves retrieving the instruction from main memory, while the Execute phase carries out the instruction's defined operation.
The section further explains the format of instructions, emphasizing the significance of operand references and opcode structures for effective programming. Key concepts like the CPU's accumulator-based architecture are introduced, along with an overview of CPU registers such as the Program Counter (PC) and Instruction Register (IR). Additionally, it touches on the various levels of programming languages, providing insight into the abstraction levels from machine code to high-level languages.
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Objectives of the Unit
Chapter 1 of 3
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Chapter Content
So, the Unit Objective of this particular unit is. Objective 1 we have to define it like that illustrate the execution of a program in a processor. So this is in Analysis level. That means, once you get a program then you will able to analyse exactly what task is performed by this particular program and how it is going to execute in a computer.
Objective 2 describe the format of Instruction. So, program is nothing but a set of instruction which will be executed in sequence. So, we are going to see; what is the format of instruction that we are having in the Instruction set of the processor. It is slightly in the design level in the higher level. Once you know the principal then you will be able to design an Instruction set for a processor.
Objective 3 explain different level of programming languages. So in a knowledge level just we are going to give information what are the different kinds of programming language we have in for computer programming. So, it is in the knowledge level just we will give the brief idea about it.
Detailed Explanation
The objectives of this unit are aimed at achieving fundamental understanding about the execution of programs in a computer system. The first objective focuses on the illustration of program execution within a processor. This involves understanding how a given program is executed and what task it accomplishes, which falls into the analysis level of learning. The second objective deals with the format of instructions, highlighting that instructions are the building blocks of programs that execute sequentially. Learning this enhances the ability to design instruction sets, which relates to design-level learning. The third objective introduces different types of programming languages, imparting knowledge about their classifications, helping students understand the spectrum of programming paradigms.
Examples & Analogies
Consider cooking in a kitchen. Just like a recipe outlines the steps to create a dish, a program in a computer is a set of instructions the computer must follow. Understanding how to execute that recipe (program) and knowing how to modify it for different dishes (instructions) helps you become a better cook (programmer). Each type of dish represents different programming languages, each with its own style and flavor.
Components of a Computer for Program Execution
Chapter 2 of 3
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Chapter Content
Now, in this particular module we have discuss about the working principle of Computers and the basic Components of the Computer. In the top level view of Computer Components are coming like that the main Component of a Computer is the processor, which is your Central Processor Unit. So, this CPU is going to perform our task depending on the program that we are going to execute.
But, the processor cannot work alone. So, we have to connect the Main Memory which is the storage device because processor works on von Neumann stored program principle. So we have to store our program and data in the Memory. So this is the Main Memory component. Here we are having the program just we are writing as Instruction and in some Memory location we have our data. So, processor works with the contents of the Main Memory, but how to take the information to the Main Memory and how we are going to get the result to the users. For that we need some I/O devices Input Output devices.
Detailed Explanation
This chunk explains the essential components required for a computer to execute a program. The Central Processing Unit (CPU) is identified as the main component, responsible for executing tasks according to the provided program. However, the CPU relies on other components like Main Memory, where the data and instruction set reside, following the von Neumann architecture which emphasizes a stored-program concept. The necessity of Input/Output devices is also highlighted, as they facilitate data transfer between the computer's memory and the user. This holistic view is vital for understanding how a computer system operates seamlessly from receiving input to executing a program and outputting results.
Examples & Analogies
Think of a CPU as a chef in a restaurant. The Main Memory is like the pantry where ingredients (data) are stored, and the Input/Output devices are like the waiters who take orders (input) from customers and deliver the finished dishes (output) back to them. Just as a chef cannot work without access to ingredients or the assistance of waiters, a CPU cannot operate effectively without memory and I/O devices.
Instruction Cycle
Chapter 3 of 3
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Chapter Content
So, we know that while going to execute an Instruction that Instruction Cycle is having basically 2 phase mainly 2 phase. One is your Fetch, second one is Execute and we have seen in the Fetch Cycle what we are going to do we are going to Fetch the Instruction from the Memory and going to bring it to the processor and once we get the Instruction our job is to execute that particular Instruction. So, we are going to execute that particular Instruction inside the processor.
Detailed Explanation
This section introduces the fundamental operation of executing instructions in a computer system termed as the Instruction Cycle. The cycle consists of two critical phases: Fetch and Execute. In the Fetch phase, the CPU retrieves an instruction from the main memory, bringing it to the processor for processing. Once fetched, in the Execute phase, the CPU performs the action specified by the instruction. This structured approach allows the CPU to manage and process numerous instructions sequentially, ensuring a logical workflow. Understanding this cycle is foundational for grasping how computers function at the operational level.
Examples & Analogies
Imagine making a telephone call where fetching a phone number is like the Fetch phase (you look it up), and actually dialing and talking to the person is like the Execute phase (you perform the action). Just as you need both steps to successfully communicate, the CPU requires both the Fetch and Execute steps to run programs.
Key Concepts
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Instruction Cycle: The process of fetching and executing instructions in the CPU.
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Opcode: The code that specifies which operation to perform.
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Operand: The reference or direct data associated with the opcode for execution.
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Accumulator: A special register used to store intermediate results during calculations.
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Program Counter: Indicates the memory address of the next instruction to execute.
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Instruction Register: Holds the instruction currently in execution.
Examples & Applications
In a simple program to add two numbers, instructions could be: Load the first number, add the second number, and store the result.
For a hexadecimal instruction 1940, the opcode 1 could mean 'load', and 940 could mean 'address in memory'.
Memory Aids
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Rhymes
Fetch to start, Execute the part; PC's the compass, IR is smart.
Stories
Imagine a factory where raw materials (fetch) come in, then workers (execute) create products. The assembly line (PC) tells the next step, while the basket (IR) holds what’s being worked on.
Memory Tools
F.E. = Fetch and Execute to remember the phases.
Acronyms
P.I.R. = Program Counter, Instruction Register, Accumulator.
Flash Cards
Glossary
- Instruction Cycle
The standard process in computing where an instruction is fetched and executed.
- Opcode
The part of an instruction that specifies the operation to be performed.
- Operand
The part of an instruction that specifies the data or address upon which the operation is to be performed.
- Accumulator
A register within the CPU that stores intermediate results of computations.
- Program Counter (PC)
A CPU register that keeps track of the address of the next instruction to be fetched.
- Instruction Register (IR)
A register that holds the currently executing instruction.
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