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466
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1 <chapter>
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2 <title>C Standard Library</title>
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3 <para>
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4 The Standard Library contains functions which fall into two
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5 classes: high-level I/O and convenience.
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6 </para>
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468
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7 <para>
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8 The high-level I/O functions provide facilities that are
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9 normally considered part of the definition of other languages; for
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10 example, the FORMAT "statement" of Fortran. In addition, automatic
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11 buffering of I/O channels improves the speed of file access because
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12 fewer system calls are necessary.
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13 </para>
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610
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14 <para>
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15 The high-level I/O functions should not be confused with the
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16 low-level system calls with similar names. Nor shoul "file
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17 pointers" be confused with "path numbers". The standard library
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18 functions maintain a structure for each file open that holds status
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19 information and a pointer into the files buffer, A user program
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20 uses a pointer to this structure as the "identity" of the file
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21 (which is provided by "fopen()"), and passes it to the various
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22 I/O functions. The I/O functions will make the low-level system
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23 calls when necessary.
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24 </para>
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25 <para>
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26 <emphasis>Using a file pointer in a systen call, or a path number in a
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27 Standard Library call</emphasis>, is a common mistake among beginners to C and,
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28 if made, will be sure to <emphasis>crash your program.</emphasis>
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29 </para>
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30 <para>
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31 The convenience functions include facilities for copying,
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32 comparing, and concatening strings, converting numbers to strings,
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33 and doing the extra work in accessing systen information such as the
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34 time.
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35 </para>
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36 <para>
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37 In the page which follow, the functions available are
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38 described in terms of what they do and the parameters they expect.
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39 The "USAGE" section shows the name of the function and the type
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40 returned (if not int). The declaration of arguments are shown as
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41 they would be written in the function definition to indicate the
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42 types expected by the function. If it is necesary to include a
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43 file before the function can be used, it is shown in the "USAGE"
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44 section by "#include <filename>".
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45 </para>
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46 <para>
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47 Most of the header files that are required to be included, must
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48 reside in the "DEFS" directory on the default system drive. If the
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49 file is included in the source program using angle bracket
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50 delimiters instead of the usual double quotes, the compiler will
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51 append this path name to the file name. For example, "#include <stdio.h>"
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52 is equivalent to "#include </d0/defs/stdio.h>", if "/d0" is
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53 the path name of the default system drive.
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54 </para>
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55 <para>
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56 <emphasis>Please note</emphasis> that if the type of the valye returned by a
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57 function is not INT, you should make a pre-declaration in your
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58 program before calling it. For example, if you wish to use
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59 "atof()", you should pre-declare by having "double atof();"
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60 somewhere in your program before a call to it. Some functions
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61 which have associated header files in the DEFS directory that
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62 should be included, will be pre-declared for you in the header. An
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63 example of this is "ftell()" which is pre-declared in "stdio.h". If
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64 you are in any doubt, read the header file.
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65 </para>
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466
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66
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67 &atofref;
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570
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68 &fcloseref;
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466
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69 &feofref;
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70 &findstrref;
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71 &fopenref;
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72 &freadref;
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73 &fseekref;
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74 &getcref;
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75 &getsref;
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76 &isalpharef;
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77 &l3tolref;
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78 &longjmpref;
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79 &mallocref;
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80 &mktempref;
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472
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81 &printfref;
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466
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82 &putcref;
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83 &putsref;
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84 &qsortref;
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85 &scanfref;
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86 &setbufref;
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87 &sleepref;
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88 &strcatref;
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89 &systemref;
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90 &toupperref;
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91 &ungetcref;
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92 </chapter>
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