Why is Unix written in C instead of C++?
This article mainly explains why Unix is written in C instead of C++. Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Now let the editor take you to learn why Unix is written in C instead of C++.
Some people will always say that C++ is not much more functional than C, but also has more functions. So why is Unix written in C instead of the more powerful C++? The obvious answer to why Unix is written in C instead of C + + is that C + + was born after C. Another reason is that the C language may actually have been invented to support the development of Unix.
The origin of C is closely related to the development of Unix OS. When the team migrated Unix to PDP- 11:00, it was still in the process of being assembled. Thompson and Ritchie want to use high-level languages in system programming so that programmers can express concepts clearly without having to bind to the architecture of a computer, but efficiently. Unix is implemented in a high-level language, thus breaking the idea that a system must be written in assembly language and that the system must be associated with a specific computer design, word length, or architecture. And for the first time, the entire programming environment, including file systems, kernels, application packages, utilities, and user interfaces, was moved to a completely different type of machine.
Thompson and Ritchie developed a programming language called "B" as early as 1969, which is essentially a simplified version of BCPL. Basically, BCPL removed unnecessary components to implement the storage capacity of minicomputers at the time (BCPL is a simplification of CPL, which itself is a simplification of Algol 60). Thompson and Ritchie are considering rewriting Unix in B language. However, B is unable to take advantage of some of the functions of PDP-11, especially byte addressing, which leads to the development of the "C" programming language. The name of C is simply chosen as the next letter after B.
The development of C began with the PDP-11 Unix system in 1972 and first appeared in Version 2 Unix. A large part of Unix is rewritten in C. Feedback from Unix developers is very helpful to C language development. The C language "merges with one of the system rewrites, so it is very suitable for writing systems". By 1973, with the addition of the "structure" type, C had become so powerful that most Unix kernels now use C. Unix became one of the first OS kernels implemented in non-assembly language.
Unix was first formally introduced to the outside world at the 1973 Symposium on operating system principles, where Ritchie and Thompson published a paper. This led to system requirements, but under the 1956 settlement agreement, AT&T (the parent company of Bell Labs) was prohibited from engaging in any business other than "public carrier communications services" in resolving antitrust cases. As a result, Unix cannot become a product. Bell Labs instead delivers the system at media and transportation costs.
Until then, however, Unix could only run on DEC systems. As more operating systems are rewritten in C (and C is extended to accommodate this situation), portability has also improved. In 1977, Bell Labs purchased Interdata 8 OS 32, which aims to port Unix to computers that are as different from PDP-11 as possible, thus making Unix more machine-independent in the process, thus realizing Thompson's dream of OS portability. All code specific to PDP-11 has been removed from the kernel and rewritten to make the transfer of Unix easier. After Interdata testing, they moved the Unix to the IBM / 370 mainframe. Through each trial, they learned more about Cjournal Unix and general portability. Gradually, Unix was ported to many other hardware systems, including Intel 8086-based computers, UNIVAC 1100 and so on.
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