Code Libraries - Computerphile

TL;DR

A code library is a collection of reusable routines that lets programmers use existing code instead of rewriting common functions. In C, routines such as printf, scanf, and file I/O can be collected and incorporated through inclusion or linking, while compilation converts the resulting program into machine code. Read on to understand inclusion, static and dynamic linking, and why libraries remain separate from programming languages.

Transcript

All a library is, is a series of code routines that you're going to reuse. So rather than actually writing it yourself, you'll go and get it from something that's already been written: a code library. So that's where the idea comes from, you're reusing blocks of code that have come from somewhere else. Implementationly, you can do that in many diff... Read More

Key Insights

• 👨‍💻 Code libraries are reusable blocks of code that help save time and effort in software development.
• 🍻 They can be included in programs through static or dynamic linking.
• 👨‍💻 The use of code libraries improves efficiency by avoiding code duplication and leveraging optimized solutions.
• 👨‍💻 Code libraries can be written in different languages and used by programs in various languages.
• 📚 Libraries can be specialized for specific tasks, such as file I/O or image recognition.
• 👨‍💻 Including code libraries in programs simplifies development and makes the codebase more manageable.
• 👨‍💻 The compilation and linking processes ensure that library code is converted into machine code and integrated with the program.

Questions & Answers

Q: What is a code library?

A code library is a collection of code routines intended for reuse in different programs. It lets programmers obtain already-written blocks of code instead of implementing the same routines again.

Q: Why do programmers use code libraries?

Programmers use libraries because many programs need the same routines, such as printf, scanf, and file I/O. Collecting those routines avoids repeated copying and keeps individual source files from becoming huge and difficult to navigate.

Q: What kinds of routines can a code library contain?

A library can group routines that perform related, useful tasks. The examples given include printing with printf, keyboard input with scanf, file I/O, and image recognition.

Q: How can a C program include reusable code from another file?

C can use an include instruction to copy another file's contents into the program at that point. This is text substitution, comparable to concatenating the files before the compiler processes the whole program.

Q: What happens to library routines when a program is compiled?

The compiler takes the program's code and converts it into machine code. When reusable source is included through text substitution, the compiler processes it as part of the whole program.

Q: What is the difference between static and dynamic linking?

Static linking combines library code with the program during compilation, producing a single binary file. Dynamic linking delays the linking process until the program is loaded and allows different library versions to be used.

Q: Why aren't common library functions built into the programming language itself?

A language only needs the foundations required to write the desired functionality; operations such as printing can be implemented separately. Keeping the language simple also makes its compiler easier to write and its code easier to check.

Q: How did limited computer memory support keeping libraries separate from C?

The transcript notes that 64k was considered a luxury on the computers for which C was developed. Under those constraints, keeping the language and compiler small made sense instead of building every useful operation into the language.

Summary & Key Takeaways

• A code library is a collection of prewritten code routines that can be reused in different programs.

• These libraries are used to avoid rewriting code and improve efficiency in software development.

• Code libraries can be included in programs through static or dynamic linking.