8.12 Chapter Summary

This chapter covered these topics:

• the difference between high and low-level considerations
• implementation dependent and implementation defined items
• about binary, octal, and hexadecimal number systems
• about units of computer storage
• about some high level access to low-level facilities in Modula-2
• about the module SYSTEM
• about type transfer functions CAST (unsafe) and VAL (safe)
• about generic procedures
• what is a logical file, a program file and a physical file
• about sequences, streams, and channels
• about sequential and random access files
• how to manipulate files with sequential and restricted stream modules
• about raw input and output
• some of the inner workings of lower level ISO modules
• one method of using the device driver TermFile

It included discussion of the following Modula-2 items:

Symbols:
H (Hexadecimal numeral indicator)
B (Octal numeral indicator)

Imports:
Standard:

• From SYSTEM:
  WORD, ADDRESS, BYTE ADR, CAST BITSPERLOC, LOCSPERWORD, LOCSPERBYTE ADDADR, SUBADR, DIFADR, MAKEADR
• From SeqFile:
  ChanId, OpenRead, OpenWrite, OpenAppend, Close, Reread, Rewrite
• From StreamFile:
  Open, Close
• From RawIO:
  Read, Write
• From TermFile:
  ChanId, Open, OpenResults, read, echo, Close
• From one or more modules:
  • the flags:
    read, write, text, raw, old, echo
  • the procedure:
    OpenResults
  • the type:
    ChanId
• From IOResult
  ReadResult, ReadResults;
• From IOChan:
  Look, Skip, SkipLook, TextRead, RawRead, WriteLn, TextWrite, RawWrite
• From StdChans:
  StdInChan, StdOutChan, StdErrChan, NullChan, InChan, OutChan, ErrChan, SetInChan, SetOutChan, SetErrChan;

• From Events:
  EventRecord, WaitNextEvent, GetCaretTime, keyDown, cmdKey, everyEvent, keyDownMask;
Non-Standard:
• From Filer/FileSystem/Files:
  File, Open, Create, Close, FileErr, FileDone, ReadChar, WriteChar, ReadWord, ReadBytes, WriteByte, WriteWord, WriteBytes
• From TextIO (non-standard):
  WriteChar, WriteString, WriteLn, WriteInt, WriteCard, WriteReal ReadChar, ReadString, ReadCard, ReadInt, ReadReal,
• From Keyboard:
  Read, BusyRead;

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