# 3.1 Computer Program A computer program is a set of well-defined instructions that a computer can execute to solve a specific problem. It interacts with the user for input, processes the data according to its code, and delivers a result. An **Algorithm** is a step-by-step procedure for calculations or problem-solving. A simple program may be based on a single algorithm, while complex programs can contain multiple algorithms for various tasks. For more on how these are developed, see . ## Program Execution The execution of a computer program follows a specific cycle: 1. **Loading**: The program is loaded from storage (e.g., a hard drive) into the *main memory* (RAM). The data the program will operate on is also loaded into main memory. 2. **Fetching**: The processor (CPU) fetches one instruction at a time from the main memory. 3. **Execution**: The processor executes the fetched instruction. 4. **Repeat**: This fetch-execute cycle repeats until all instructions in the program have been completed. ## Types of Computer Programs Computer programs are generally categorized based on their execution model. | Program Type | Description | Example | | :--- | :--- | :--- | | **Interactive Program** | Accepts input directly from a user or another program during its execution. | A web browser, a word processor, or a video game. | | **Batch Program** | Executes a set of commands (a "batch" or "job") sequentially without user interaction. It processes them one after another and halts when the queue is empty. | A print job queue, where documents are printed one by one. | ## Programming Languages and Translation Programs are written in *programming languages*, which provide a set of rules (*syntax*) and *keywords* to create instructions (code). This human-readable code must be translated into machine-readable code for the processor to execute. - **Machine Language**: The low-level language consisting of binary data that a computer's processor can directly understand and execute. For details on how data is represented at this level, see . ### Translators: Compilers vs. Interpreters | Translator | Process | Output | Examples | | :--- | :--- | :--- | :--- | | **Compiler** | Scans and translates the *entire source code* at once, checking for syntax errors before execution. | Creates a standalone executable *object file* in machine language. | C++, Java, Assembly Language, Fortran. | | **Interpreter** | Translates and executes the source code *line-by-line*. | No separate object file is created; translation happens during runtime. | Python, JavaScript, Ruby. | Python is a popular interpreted language. You can learn more about it in .