64-bit refers to sixty-four binary (0 or 1) units of integer data. This allows for up to 18,446,744,073,709,551,616 combinations of values.
- 64-bit color, is typically split into four sets of 16-bit values for 65,536 levels per RGBA channel (red, green, blue, and alpha). The three 16-bit RGB values deliver 281,474,976,710,656 unique colors, the same as 48-bit color, but with the addition of 65,536 levels of transparency defined by the alpha channel. This range is also known as "deep color".
- 64-bit sound allows for a range of up to 18,446,744,073,709,551,616 values (−9,223,372,036,854,775,808 to +9,223,372,036,854,775,807) per sample (Hertz).
- 64-bit addressing allows for access to up to 18,446,744,073,709,551,616 bytes, or 18.4 exabytes of data.
- 64 bits of data make 8 bytes, referred to by programmers as a quadword.
- Mac OS X Tiger (10.4), the first version of Mac OS X to implement partial support for 64-bit applications.
- Mac OS X Snow Leopard (10.6), the first version to implement full 64-bit support, while maintaining backwards compatibility with 32-bit applications.
- macOS Catalina (10.15), the first version of macOS to operate solely in 64-bit, dropping support for 32-bit applications.
- PowerPC G5, the first 64-bit processor used by Apple Computer, in the Power Macintosh G5 computer.
- QuickTime X, the 64-bit successor to QuickTime.
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