COS 333: Chapter 2, Part 2

Summary

This lecture continues the exploration of high-level programming languages, covering Algol 60, COBOL, BASIC, PL1, APL, and SNOBOL. Algol 60 was influential but not widely adopted due to its complexity and lack of input/output support. COBOL was designed for business applications and emphasized English-like syntax. BASIC aimed to be easy for non-science students, leveraging time-sharing systems. PL1 sought to unify scientific and business computing. APL introduced powerful array operations but suffered from readability issues. SNOBOL focused on string manipulation and text processing. The lecture emphasizes the historical context and unique features of each language.

Takeaways

• 📚 The script discusses the evolution and development of major high-level programming languages, focusing on their historical context and design goals.
• 🔍 It provides an overview of Algol 60, highlighting its influence on subsequent languages and its goal of being a universal, machine-independent language, despite its limited adoption due to lack of I/O operations and string handling.
• 💼 COBOL is presented as the first widely adopted language for business applications, designed to be English-like and easy to use, with a focus on a detailed data division but a less powerful procedure division.
• 👶 BASIC (Beginner's All-Purpose Symbolic Instruction Code) was created with novice programmers in mind, emphasizing ease of learning, use, and a friendly approach for non-science students.
• 🔢 PL/1 (Programming Language 1) aimed to be a universal language applicable to both scientific and business computing, introducing features like concurrency, exception handling, and pointer data types, but was criticized for its complexity.
• 📊 APL (A Programming Language), also known as 'Apple', is noted for its expressive and powerful operators, especially for array operations, but is often considered hard to read due to its unique symbols and compact syntax.
• ❄️ Snowball is recognized as a dynamic language designed for text processing, featuring custom notation for string pattern matching, though its use is now limited compared to other languages.
• 🔑 The script emphasizes the importance of understanding the environment and needs that led to the development of each language, such as FORTRAN for scientific computing and COBOL for business applications.
• 🛠️ The design goals of each language are highlighted, showing how they were tailored to the specific requirements and limitations of their time, such as Algol 60's focus on algorithm description and machine independence.
• 📈 The script also discusses the challenges faced by some languages, such as Algol 60's lack of widespread adoption due to its initial design oversights and the competition with established languages like FORTRAN.
• 🔬 The development of programming languages is portrayed as an iterative process, with later languages building upon the innovations and addressing the shortcomings of their predecessors.

Q & A

What was the significance of ALGOL 60 in the history of programming languages?

ALGOL 60 was significant because it was an influential programming language that affected the development of most other high-level programming languages that followed it. It was designed to be machine-independent, aiming to be a universal programming language, and introduced many revolutionary concepts such as block structures with local scope for variables and sophisticated parameter passing mechanisms.

Why was COBOL designed and what were some of its unique features?

COBOL was designed as the first programming language intended for business applications. It was meant to be easy to use and understand, even for those without a strong technical background. Unique features included support for hierarchical data structures, long names with hyphens for better readability, and a separation of data and code with a detailed data division and a procedure division.

What was the purpose behind the creation of BASIC and how did it differ from other programming languages at the time?

BASIC, which stands for Beginner's All-Purpose Symbolic Instruction Code, was created to be an easy-to-learn and user-friendly language for non-science students. It differed from other languages by focusing on fast turnaround for homework assignments, being free and not vendor-specific, and treating user time as more important than computer time.

How did time-sharing systems influence the development and use of BASIC?

Time-sharing systems allowed multiple users to interact with a single powerful computer and its resources simultaneously. This enabled BASIC users to get real-time feedback on errors in their programs, promoting an iterative and interactive programming experience that was not possible with batch processing systems.

What was the goal of PL/1 and how did it attempt to achieve universality in programming?

PL/1 aimed to be a universal programming language applicable to different programming domains, particularly scientific computing and business computing. It attempted to achieve universality by incorporating features from both domains and by being designed to work with the IBM System/360 line of computers, which were intended for both scientific and business applications.

What are some of the major contributions of PL/1 to programming language design?

PL/1 introduced several major contributions, including the first unit-level concurrency, the first exception handling mechanism, the first pointer data type, and support for array cross-sections. These features influenced the design of subsequent programming languages.

Why was APL considered a very expressive programming language despite its complexity?

APL was considered very expressive because it had a large set of powerful operators that worked for both scalar and array values, allowing for the compact representation of complex operations such as matrix inversion and transposition. However, this also made APL programs difficult to read due to the large number of non-standard operators.

What is the primary focus of the Snowball programming language and how does it differ from other languages in string manipulation?

Snowball is primarily a string manipulation language designed for text processing. It differs from other languages by using its own custom notation for string pattern matching instead of regular expressions, which was a revolutionary idea at the time of its creation.

What were some of the challenges faced by the designers of ALGOL 60 in terms of implementation and adoption?

Some challenges faced by the designers of ALGOL 60 included the lack of input/output operations and string handling in the language specification, which limited its portability and实用性. Additionally, the formal syntax description in Backus-Naur Form (BNF) was considered confusing at the time, which may have hindered adoption.

How did the design goals of FORTRAN and COBOL differ, and what impact did these differences have on their respective uses?

FORTRAN was designed with a focus on scientific computing and efficient compiler performance, making it suitable for technical users. In contrast, COBOL was designed to be more English-like and easy to use for business applications, even at the cost of being less powerful. These differences led to FORTRAN being widely used in scientific fields and COBOL becoming the dominant language for business applications.