notebook/notes/c/declarations.md

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---
title: Declarations
TARGET DECK: Obsidian::STEM
FILE TAGS: c
tags:
- c
---
## Overview
Signed | Unsigned | 32-bit | 64-bit
----------- | -------------- | ------ | ------
signed char | unsigned char | 1 | 1
short | unsigned short | 2 | 2
int | unsigned | 4 | 4
long | unsigned long | 4 | 8
char * | - | 4 | 8
float | - | 4 | 4
double | - | 8 | 8
Fixed width data integral types (e.g. `int32_t`) can be found by including `<stdint.h>`.
%%ANKI
Cloze
The {`<stdint.h>`} header file contains {fixed width data integral types}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
What does the "width" of an integer type refer to?
Back: The number of bits used to represent its value.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
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%%ANKI
What two variants does a C integral type declaration have?
Back: Signed and unsigned.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
What does it mean for an integer to be "signed"?
Back: It can represent negative, zero, and positive values.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
What does it mean for an integer to be "unsigned"?
Back: It can only represent nonnegative values.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
2024-02-11 14:57:30 +00:00
%%ANKI
Basic
How large is a word?
Back: This is a machine-dependent value.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
What word sizes are typical nowadays?
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Back: 32- and 64-bit word sizes.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
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%%ANKI
Cloze
`char` *typically* represents {1} byte(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Cloze
`short` *typically* represents {2} byte(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Cloze
`int` *typically* represents {4} bytes(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017215-->
END%%
%%ANKI
Cloze
`unsigned` *typically* represents {4} bytes(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Cloze
`long` *typically* represents {8} bytes(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017222-->
END%%
%%ANKI
Cloze
`char *` *typically* represents {8} bytes(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017224-->
END%%
%%ANKI
Cloze
`float` *typically* represents {4} bytes(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017227-->
END%%
%%ANKI
Cloze
`double` *typically* represents {8} bytes(s) on a 64-bit platform.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017229-->
END%%
%%ANKI
Basic
Is declaration `int` signed or unsigned?
Back: Signed.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017232-->
END%%
%%ANKI
Basic
How is declaration `unsigned` written more precisely?
Back: `unsigned int`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017234-->
END%%
%%ANKI
Basic
Is declaration `long` signed or unsigned?
Back: Signed.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1707493017237-->
END%%
%%ANKI
Basic
Is declaration `char` signed or unsigned?
Back: Unknown.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Cloze
{1:`float`} has {2:4} byte precision whereas {2:`double`} has {1:8} byte precision.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Cloze
The C standard sets {1:lower bounds} on data type ranges, but does not set {1:upper bounds} (except with fixed-size types).
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
Pointers have the same size as the machine's word size since it should be able to refer to any virtual address.
%%ANKI
Basic
*Why* does a pointer's size match the machine's word size?
Back: Because it should be able to refer to any virtual address.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
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## References
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* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.