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P.S. I synthesize and re-write in my own words what books teach, write any example programs they contain, solve all exercises they offer, and comment cursively. I list pages done vs total pages, including any roman and appendix numbering.
SCO Ed6 Page7 - Phase1 0007/2384
To sum up: some level 3 instructions are interpreted by the operating system and some directly by the data path controller, whether that is done by the microprogram, or embedded in the hardware. Because of these different sources of instructions coming together at the same level, we call it a hybrid level. Onward the book will call the hybrid level the operating system level.
Between level 3 and 4 we can see a clear break.
The main point to understand about computer organization is that computing consists of layers of abstraction and interpretation/translation, which are brought forth by different kinds of software programs and hardware operations.
(but in essence, there is only hardware, and all the abstraction happens within the human mind)
SCO Ed6 Page7 - Phase1 0007/2384
To sum up: some level 3 instructions are interpreted by the operating system and some directly by the data path controller, whether that is done by the microprogram, or embedded in the hardware. Because of these different sources of instructions coming together at the same level, we call it a hybrid level. Onward the book will call the hybrid level the operating system level.
Between level 3 and 4 we can see a clear break.
- Levels 0 to 3
Are not normally accessed by the average programmer, rather programs like interpreters and translators are running on those levels, to support applications of the higher levels. Such level 3 programs are written by system programmers. These people specialize in designing and implementing virtual machines.
Level 2 and 3 are always interpreted. Levels 1. 2 and 3 code is always numeric. Easy to read for machines but hard to read for humans.
Level 2 and 3 are always interpreted. Levels 1. 2 and 3 code is always numeric. Easy to read for machines but hard to read for humans.
- Level 4 and up
Are used by application programmers. These levels are usually translated but sometimes also interpreted. These programs are human readable to different degrees.
Level 4: assembly language (ASM), is a symbolic form of the levels below and is particularly well suited to write programs that levels 1-3 can understand, while still being reasonably readable to humans. Assembly is first translated to the destined level by the assembler program and then there interpreted by the respective virtual machine or directly by the hardware.
Level 5 consists of the high level languages, used for applications with specific functionality. Many exist: C, C++, Java, Perl, Python, PHP, etc., etc. These are most often translated to level 4 or 3 by translaters called compilers, but sometimes also interpreted: Java, for example is first translated to Java byte code, an ISA-like language, which is then interpreted. On level 5 here are also specialized interpreters for specific application domains, like for example symbolic mathematics.
Level 4: assembly language (ASM), is a symbolic form of the levels below and is particularly well suited to write programs that levels 1-3 can understand, while still being reasonably readable to humans. Assembly is first translated to the destined level by the assembler program and then there interpreted by the respective virtual machine or directly by the hardware.
Level 5 consists of the high level languages, used for applications with specific functionality. Many exist: C, C++, Java, Perl, Python, PHP, etc., etc. These are most often translated to level 4 or 3 by translaters called compilers, but sometimes also interpreted: Java, for example is first translated to Java byte code, an ISA-like language, which is then interpreted. On level 5 here are also specialized interpreters for specific application domains, like for example symbolic mathematics.
The main point to understand about computer organization is that computing consists of layers of abstraction and interpretation/translation, which are brought forth by different kinds of software programs and hardware operations.
(but in essence, there is only hardware, and all the abstraction happens within the human mind)
