User
•Software Development
•What is code
•Types of code:
Machine code
Assembly code
Low level code
High level code
•Development tools for translating code to machine code:
Assembler
Linkers
Compilers
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Software Development:
Software development is the process of designing, creating, testing, and maintaining software applications, frameworks, or other software components. It involves a systematic approach to building software that meets specified requirements and addresses user needs.
What is Code:
Code refers to the set of instructions written in a programming language that a computer can understand and execute to perform specific tasks. It is the fundamental building block of software development and encompasses a wide range of instructions and statements that control the behavior of a computer program.
Types of Code:
Machine Code:
Machine code, also known as binary code, is the lowest level of code that directly represents instructions executed by a computer's central processing unit (CPU). It consists of binary digits (0s and 1s) that correspond to specific machine-level operations.
Assembly Code:
Assembly code is a low-level programming language that uses symbolic instructions representing machine-level operations. It is more readable than machine code but still closely tied to the architecture of the target CPU. Assembly code is often used for tasks requiring precise control over hardware resources or performance optimization.
Low-Level Code:
Low-level code encompasses both machine code and assembly code. It typically refers to code that interacts closely with hardware and operates at a level close to the machine's architecture. Low-level code is efficient but often requires expertise in hardware-specific details.
High-Level Code:
High-level code is written in programming languages that are more abstracted from the hardware and closer to human language. Examples include languages like Python, Java, C++, and many others. High-level code is easier to read, write, and maintain than low-level code, but it requires translation (compilation or interpretation) into machine code for execution.
Development Tools for Translating Code to Machine Code:
Assembler:
An assembler is a software tool that translates assembly code into machine code. It takes human-readable assembly instructions and converts them into binary machine language instructions that can be executed by the CPU. Assemblers are essential for programming at the low-level and are used in embedded systems, device drivers, and other performance-critical applications.
Linkers:
Linkers are tools that combine multiple object files generated by compilers and assemblers into a single executable program or library. They resolve references between different parts of the code, such as function calls and variable accesses, ensuring that the final executable is complete and can be loaded and executed by the operating system.
Compilers:
Compilers are software tools that translate high-level code written in programming languages like C, C++, Java, or Python into machine code. They perform several stages of translation, including lexical analysis, syntax parsing, optimization, and code generation. The output of a compiler is typically an executable program or intermediate code that can be further processed or executed. Compilers enable developers to write code in a more abstracted and expressive manner while still producing efficient machine code for execution.
User
•Runtime Environment
•Definition of a runtime environment or runtime system
What do RTE’s provide
Types of RTE
Development tools’ relationship to the RTE:
•What kind of code does a web browser require to run JavaScript
•What kind of code does the Java JVM require to run Java
•What kind of code does Linux or Windows require to run C
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Runtime Environment:
Definition of a Runtime Environment or Runtime System:
A runtime environment (RTE) or runtime system refers to the infrastructure and resources required to execute software programs during runtime. It provides essential services and support for running applications, including managing memory, executing code, handling input/output operations, and interfacing with the underlying hardware and operating system.
What RTEs Provide:
Execution Environment: RTEs provide the necessary runtime environment for executing compiled or interpreted code. This environment includes memory allocation, process management, and other runtime services needed for program execution.
Abstraction Layer: RTEs abstract away the complexities of hardware and operating system interactions, allowing developers to write code that can run on different platforms without modification.
Libraries and APIs: RTEs often include libraries and application programming interfaces (APIs) that provide access to various system resources and functionalities, such as file I/O, networking, GUI components, and more.
Error Handling: RTEs typically handle runtime errors and exceptions, providing mechanisms for debugging, error reporting, and recovery during program execution.
Types of RTE:
Operating System Runtime Environment: The operating system provides a runtime environment for executing applications and managing system resources. It includes services such as process scheduling, memory management, file system access, and device drivers.
Virtual Machine Runtime Environment: Virtual machines, such as the Java Virtual Machine (JVM), provide a runtime environment that abstracts the underlying hardware and operating system, allowing platform-independent execution of bytecode or intermediate code.
Web Browser Runtime Environment: Web browsers provide a runtime environment for executing client-side scripts, such as JavaScript, within web pages. They include JavaScript engines, DOM manipulation APIs, and other web platform features.
Development Tools' Relationship to the RTE:
Development tools play a crucial role in creating software that can run within different runtime environments. They facilitate the writing, testing, and deployment of code, ensuring compatibility with the target RTE.
What Kind of Code Does a Web Browser Require to Run JavaScript:
A web browser requires JavaScript code written in plain text format. JavaScript is a high-level scripting language that is interpreted by the browser's JavaScript engine at runtime. Web browsers provide a runtime environment for executing JavaScript code within web pages, including features for manipulating the Document Object Model (DOM), handling events, and interacting with web APIs.
What Kind of Code Does the Java JVM Require to Run Java:
The Java Virtual Machine (JVM) requires Java bytecode to execute Java programs. Java source code is compiled into platform-independent bytecode by the Java compiler. The JVM provides a runtime environment for executing bytecode on any system that has a compatible JVM implementation installed.
What Kind of Code Does Linux or Windows Require to Run C:
Linux or Windows operating systems do not directly require specific code to run C programs. Instead, they provide the runtime environment necessary for executing compiled C programs. C source code is compiled into machine code or executable files using a C compiler, such as GCC (GNU Compiler Collection) on Linux or Microsoft Visual C++ compiler on Windows. The resulting executable files contain machine code that can be executed by the operating system's runtime environment. The operating system provides services such as process management, memory allocation, and system calls required for running C programs.
User
•Memory Management
•Describe the address space (aka logical or virtual memory)
•Describe the layout of a process in memory
•Compare the text, heap, and stack sections
•Describe physical memory
•Compare a physical address space to the logical address space
•When can address binding occur
•How is a virtual address translated to a physical address
•Describe static relocation, segmentation
•What causes fragmentation
•Describe external fragmentation; compare swapping to compacting
•What is paging?
•Describe a page, page frame, page table
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Memory Management:
Memory management is a crucial aspect of computer systems that involves organizing and coordinating memory resources to efficiently store and retrieve data and instructions during program execution. It encompasses various techniques and mechanisms for managing both logical/virtual memory and physical memory.
Address Space (Logical or Virtual Memory):
The address space, also known as logical or virtual memory, is the abstract view of memory seen by a process. It represents the range of memory addresses accessible to a program during execution.
Each process has its own address space, which typically starts from address 0 and extends to the maximum address supported by the system.
The address space is divided into different segments, including text (code), data, heap, and stack.
Layout of a Process in Memory:
The layout of a process in memory typically includes the following sections:
Text (Code): Contains the executable instructions of the program.
Data: Includes initialized and uninitialized (BSS) data segments.
Heap: Dynamically allocated memory used for data structures such as arrays and linked lists.
Stack: Stores local variables, function parameters, return addresses, and other function call-related information.
Comparison of Text, Heap, and Stack Sections:
Text Section: Contains the executable code of the program and is typically read-only.
Heap Section: Dynamically allocated memory managed by the programmer using functions like malloc() and free(). Memory allocation in the heap is more flexible but can lead to fragmentation.
Stack Section: Managed by the system and used for storing function call-related information. Memory allocation in the stack is automatic and follows a Last-In-First-Out (LIFO) structure.
Physical Memory:
Physical memory refers to the actual hardware memory modules installed in the computer system, including RAM (Random Access Memory) and secondary storage devices like hard drives and SSDs.
The operating system manages physical memory allocation and ensures efficient utilization by mapping virtual addresses to physical memory locations.
Comparison of Physical Address Space to Logical Address Space:
Physical Address Space: Represents the actual memory addresses in hardware, as seen by the memory controller and RAM modules.
Logical Address Space: Represents the memory addresses generated by a program, which are translated to physical addresses by the memory management unit (MMU) during execution.
Address Binding:
Address binding refers to the process of associating a memory address with a specific memory location.
Address binding can occur at different stages, including compile time, load time, and execution time.
Virtual Address Translation to Physical Address:
Virtual addresses generated by a process are translated to physical addresses by the Memory Management Unit (MMU) using techniques such as paging or segmentation.
Static Relocation, Segmentation:
Static Relocation: Involves assigning fixed memory addresses to program components during the linking process. It results in absolute addresses, which can lead to issues like fragmentation and lack of flexibility.
Segmentation: Divides a program into segments (logical units) such as code, data, and stack. Each segment is assigned a base address and size, allowing for dynamic allocation and efficient memory management.
Fragmentation:
Fragmentation occurs when memory is divided into small, non-contiguous blocks, leading to inefficient memory utilization.
External Fragmentation: Occurs when free memory blocks are scattered throughout the memory space, making it challenging to allocate contiguous blocks of memory to processes.
Swapping involves moving entire processes between main memory and secondary storage to free up space.
Compacting rearranges memory contents to eliminate fragmentation by shifting allocated memory towards one end of the memory space.
Paging:
Paging is a memory management scheme that divides logical memory into fixed-size blocks called pages.
Physical memory is divided into blocks called page frames of the same size as pages.
A page table is used to map virtual pages to physical page frames, allowing for efficient memory allocation and address translation.
Page, Page Frame, Page Table:
Page: A fixed-size block of logical memory.
Page Frame: A fixed-size block of physical memory corresponding to a page.
Page Table: A data structure used by the operating system to map virtual pages to physical page frames, storing the mapping information for each page.