Programming Techniques DT143G - Lecture 3: Datatypes

Study Notes

Programmeringsteknik DT143G - Lecture 3: Datatypes

Datatypes and Manipulating Operations are covered in this lecture.
Integers are the first datatype discussed.
Integers are used to store whole numbers.
Integer size varies depending on the compiler and architecture, typically 2 bytes (-32,768 to 32,767) or 4 bytes in general (32 bits).
Unsigned integers also exist.
The lecture addresses the implications of exceeding integer ranges.
Other Integer Types
- short int uses at least 2 bytes.
- long int uses at least 4 bytes.
- long long int uses at least 8 bytes.
- Both signed and unsigned integers exist (uint).
- char (1 byte) stores characters (ASCII).
- Sizes can vary, depending on the compiler and architecture.
- A byte is 8 bits.
Real Numbers
- Real numbers (floating-point types) are used to store numbers with decimal points.
- float uses 4 bytes.
- double uses 8 bytes.
- long double uses at least 80 bits.
Real numbers: float
- float (32 bits, IEEE 754) is a floating-point number.
- It has a sign bit, exponent, and mantissa.
- The precision of float depends on the absolute value.
printf Format Specifiers
- %f for float.
- %lf for double.
- %.2f for 2 decimal places.
- %5.3f for 5 integer digits, 3 decimal digits.
- %e for scientific notation.
Mixing Datatypes
- Mixing different datatypes in operations like a + b might have unexpected results.
- Consider potential conversions or issues when handling mixed types.
- a + 1 and a + 1.0 might have different results depending on the compiler and the data types.
Conversion
- Conversion from smaller to larger datatypes is usually straightforward.
- Conversion from larger to smaller datatypes can result in data loss (e.g., losing the fractional part during conversion from float to int).
limits.h file: This file includes maximum and minimum values for integer types (e.g., INT_MAX, INT_MIN, ULONG_MAX).
Modifiers
- const: to prevent modifications to a variable’s value.
Mathematical Library
- Example C code is shown to use mathematical functions from the mathematical library: #include <stdio.h> and #include <math.h>.
- The command -lm is indicated when compiling.
Conclusion
- Understanding datatypes is essential.
- C's datatype sizes can vary, and consideration is needed in mixed datatype operations.
- Maximum and minimum values for each type should be considered.