notebook/notes/x86-64/declarations.md

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---
title: Declarations
TARGET DECK: Obsidian::STEM
FILE TAGS: x86-64
tags:
- x86-64
---
## Overview
| C Declaration | Intel Data Type | Suffix | Size (bytes) |
| ------------- | ---------------- | ------ | ------------ |
| `char` | Byte | `b` | 1 |
| `short` | Word | `w` | 2 |
| `int` | Double word | `l` | 4 |
| `long` | Quad word | `q` | 8 |
| `char *` | Quad word | `q` | 8 |
| `float` | Single-precision | `s` | 4 |
| `double` | Double-precision | `l` | 8 |
%%ANKI
Basic
What is the width of a word?
Back: 16 bits.
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 historical reason explains why a word is 16 bits?
Back: Because the 8086 that introduced x86 was 16 bits.
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 is the width of an Intel "byte"?
Back: $8$ bits
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
Which Intel data types are 1 bytes wide?
Back: Just the "byte".
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 "{byte}" Intel data type has assembly-code suffix {`b`}.
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 is the width of an Intel "word"?
Back: $16$ bits
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
Which Intel data types are 2 bytes wide?
Back: Just the "word".
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 "{word}" Intel data type has assembly-code suffix {`w`}.
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 is the width of an Intel "double word"?
Back: $32$ bits
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
Which Intel data types are 4 bytes wide?
Back: The double word and single-precision.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1711116523836-->
END%%
%%ANKI
Cloze
The "{double word/double-precision}" Intel data type has assembly-code suffix {`l`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1711116523839-->
END%%
%%ANKI
Basic
*Why* do double words have assembly-code suffix `l`?
Back: The suffix stands for "long", relative to a 16-bit word.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1711116523842-->
END%%
%%ANKI
Basic
What is the width of an Intel "quad word"?
Back: $64$ bits
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
Which Intel data types are 8 bytes wide?
Back: The quad word and double-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 "{quad word}" Intel data type has assembly-code suffix {`q`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1711116523853-->
END%%
%%ANKI
Cloze
C integral declaration {`char`} corresponds to Intel data type "{byte}".
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
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END%%
%%ANKI
Cloze
C integral declaration {`short`} corresponds to Intel data type "{word}".
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
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END%%
%%ANKI
Cloze
C integral declaration {`int`} corresponds to Intel data type "{double word}".
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
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END%%
%%ANKI
Cloze
C integral declaration {`long`} corresponds to Intel data type "{quad word}".
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
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END%%
%%ANKI
Cloze
C declaration `char *` corresponds to Intel data type "{quad word}".
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
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END%%
%%ANKI
Cloze
C floating-point declaration {`float`} corresponds to Intel data type "{single-precision}".
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
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END%%
%%ANKI
Cloze
The "{single-precision}" Intel data type has assembly-code suffix {`s`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1711116523881-->
END%%
%%ANKI
Cloze
C floating-point declaration {`double`} corresponds to Intel data type "{double-precision}".
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
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END%%
%%ANKI
Basic
What is the width of an Intel "singe precision"?
Back: $32$ bits
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 two Intel data types do floating-point numbers come in?
Back: Single-precision and double-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
Basic
Assembly-code suffix `l` is used for what two Intel data types?
Back: Double words and double-precisions.
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 is the width of an Intel "double-precision"?
Back: $64$ bits
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1711116523903-->
END%%
%%ANKI
Basic
Why is it safe for double words and double-precisions to both use assembly-code suffix `l`?
Back: Floating-point code uses a different set of instructions and registers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1711116523908-->
END%%
## References
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.