21 KiB
| title | TARGET DECK | FILE TAGS | tags | |
|---|---|---|---|---|
| Types | Obsidian::STEM | c17 |
|
Overview
C has a series of basic types and means of constructing derived types from them.
Integers
Type char is special since it can be signed or unsigned depending on platform. Keep in mind regardless of its signedness, it is still considered a distinct type from both the unsigned char and signed char type.
%%ANKI
Basic
Is declaration char signed or unsigned?
Back: This is implementation-dependent.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
Narrow types cannot be used directly in arithmetic. Instead they are first promoted to a wider type. On almost every system, this promotion will be to a signed int of the same value, regardless of the signedness of the narrow type itself.
%%ANKI Basic Why are narrow types named the way they are? Back: They are considered to small to be used directly in arithmetic expressions. Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Signed narrow types are usually promoted to what larger type?
Back: A signed int.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Unsigned narrow types found are usually promoted to what larger type?
Back: A signed int.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
Unsigned
These correspond to nonnegative integer values.
| Name | Narrow | Rank |
|---|---|---|
bool |
Yes | 0 |
char (maybe) |
Yes | 1 |
unsigned char |
Yes | 1 |
unsighed short |
Yes | 2 |
unsigned int |
No | 3 |
unsigned long |
No | 4 |
unsigned long long |
No | 5 |
%%ANKI
Basic
Which basic unsigned type has the smallest rank?
Back: bool
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned type next succeeds bool in rank?
Back: unsigned char and (maybe) char.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned type next succeeds unsigned char in rank?
Back: unsigned short
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned type next succeeds unsigned short in rank?
Back: unsigned int
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned type next succeeds unsigned int in rank?
Back: unsigned long
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned type next succeeds unsigned long in rank?
Back: unsigned long long
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned type next succeeds unsigned long long in rank?
Back: N/A.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned narrow type has the highest rank?
Back: unsigned short
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which unsigned non-narrow type has the smallest rank?
Back: unsigned int
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
Signed
These correspond to possibly negative integer values.
| Name | Narrow | Rank |
|---|---|---|
char (maybe) |
Yes | 1 |
signed char |
Yes | 1 |
signed short |
Yes | 2 |
signed int |
No | 3 |
signed long |
No | 4 |
signed long long |
No | 5 |
float |
- | - |
double |
- | - |
long double |
- | - |
%%ANKI
Basic
Which basic signed type has the smallest rank?
Back: signed char and (maybe) char.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which signed type succeeds signed char in rank?
Back: signed short
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which signed type succeeds signed short in rank?
Back: signed int
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which signed type succeeds signed int in rank?
Back: signed long
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which signed type succeeds signed long in rank?
Back: signed long long
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which signed type succeeds signed long long in rank?
Back: N/A.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which signed narrow type has the highest rank?
Back: signed short
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
Which signed non-narrow type has the smallest rank?
Back: signed int
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
Literals
Negative integer literals are typed in a counterintuitive way. When the compiler sees a number of form -X, the type of X is determined before being negated. Promotion follows the first fit rule described as follows:
| Decimal | Oct/Hex |
|---|---|
int |
int |
long |
unsigned |
long long |
long |
- |
unsigned long |
- |
long long |
- |
unsigned long long |
%%ANKI Basic What is the first fit rule? Back: A specification on what type is given to an integer literal. Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
What is the signedness of a decimal integer literal?
Back: signed
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
What is the signedness of an octal integer literal?
Back: signed or unsigned.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
What is the signedness of a hexadecimal integer literal?
Back: signed or unsigned.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
The first fit rule lists what types (in order) for decimal integer literals?
Back: int, long, and long long.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
The first fit rule lists what types (in order) for octal integer literals?
Back: int, unsigned, long, unsigned long, long long, and unsigned long long.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
The first fit rule lists what types (in order) for hexadecimal integer literals?
Back: int, unsigned, long, unsigned long, long long, and unsigned long long.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
The first fit rule lists what types (in order) for hexadecimal integer literals?
Back: int, unsigned, long, unsigned long, long long, and unsigned long long.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
How does the compiler process integer literal -X?
Back: By first determining the type of X and then negating the value.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What integer literals are guaranteed signed?
Back: Decimal integer constants.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
How do we specify an octal integer literal?
Back: Prepend the literal with a 0.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Why avoid negative octal integer literals?
Back: Depending on value, the resulting type may be unsigned.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
How do we specify a hexadecimal integer literal?
Back: Prepend the literal with a 0x or 0X.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Why avoid negative hexadecimal integer literals?
Back: Depending on value, the resulting type may be unsigned.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
Octal literals are to {0} whereas hexadecimal literals are to {0x/0X}.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
How might C dangerously interpret a negative hexadecimal integer literal?
Back: Depending on the value, the resulting type may be unsigned.
Reference: Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which header file contains INT_MAX?
Back: <limits.h>
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{INT_MAX} is to signed whereas {UINT_MAX} is to 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
Basic
How does <limits.h> define INT_MIN?
Back: As (-INT_MAX - 1).
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Why is INT_MIN defined as (-INT_MAX - 1) instead of directly as e.g. -2147483648?
Back: Because 2147483648 (without -) would be sized as a non-int before being negated.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
INT_MAX is to {<limits.h>} whereas INT32_MAX is to {<stdint.h>}.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI Basic In what order does C cast size and "signedness"? Back: C casts size then signedness. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI Basic In what order does C cast "signedness" and size? Back: C casts size then signedness. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Given short sx, cast (unsigned) sx is more explicitly written as what other sequence of casts?
Back: (unsigned) (int) sx
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Given short sx, are the following two lines equivalent?
(unsigned) sx
(unsigned) (int) sx
Back: Yes. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Given short sx, are the following two lines equivalent?
(unsigned) sx
(unsigned) (unsigned short) sx
Back: No. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Given short sx, why is the following not an identity?
(unsigned) sx = (unsigned) (unsigned short) sx
Back: (unsigned) sx casts size before "signedness".
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What does "signedness" of a variable refer to?
Back: Whether the variable was declared signed or unsigned.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
Integer constants can be forced to be unsigned or to be a type with minimal width by using the following suffixes:
| Suffix | Type |
|---|---|
U |
unsigned |
L |
long |
LL |
long long |
ULL |
unsigned long long |
%%ANKI
Basic
Is an integer literal without a suffix (e.g. U) signed or unsigned?
Back: This depends on the first fit rule.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
What type is given to an integer literal without a suffix (e.g. U)?
Back: This depends on the first fit rule.
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
What suffix can be used to denote an unsigned integer literal?
Back: Case-insensitive U.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What suffix can be used to denote a long integer literal?
Back: Case-insensitive L.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What suffix can be used to denote a long long integer literal?
Back: Case-insensitive LL.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What suffix can be used to denote an unsigned long long integer literal?
Back: Case-insensitive ULL.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to integer literal -1?
Back: int
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to integer literal -1U?
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.
END%%
%%ANKI
Basic
What type is given to integer literal 1?
Back: int
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to integer literal 0x0U?
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.
END%%
Floating Point
Literals
Floating-point constants can be forced to be a type with minimal width by using the following suffixes:
| Suffix | Type |
|---|---|
F |
float |
L |
long double |
%%ANKI
Basic
What type is given to a floating-point literal without a suffix (e.g. F)?
Back: double
Reference: Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).
END%%
%%ANKI
Basic
What suffix can be used to denote a float floating-point literal?
Back: Case-insensitive F.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What suffix can be used to denote a double floating-point literal?
Back: N/A. Do not use a suffix.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What suffix can be used to denote a long double floating-point literal?
Back: Case-insensitive L.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to floating-point literal -1.0?
Back: double
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to floating-point literal -1.0F?
Back: float
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to floating-point literal -1.0FL?
Back: N/A. Invalid suffix.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to floating-point literal -1.0L?
Back: long double
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What type is given to floating-point literal -1.0LL?
Back: N/A. Invalid suffix.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
Bibliography
- Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
- Jens Gustedt, Modern C (Shelter Island, NY: Manning Publications Co, 2020).