I'm studying DX12. I came across this texture format:
DXGI_FORMAT_R8G8B8A8_UNORM
A four-component, 32-bit unsigned-normalized-integer format that supports 8 bits per channel including alpha.
It's not clear to me exactly - what values does each RGBA element store? As it is clear from the description above, these values are from 0 to 1 i.e. UNORM. But how, for example, can 1 byte R8 store a real number from 0.0f to 1.0f?
The format modifiers like _UNORM / _SNORM / _FLOAT, etc... are documented on the DXGI_FORMAT Page:
Format Modifiers
Each enumeration value contains a format modifier which describes the data type.
_UNORM
Unsigned normalized integer; which is interpreted in a resource as an unsigned integer, and is interpreted in a shader as an unsigned normalized floating-point value in the range [0, 1]. All 0's maps to 0.0f, and all 1's maps to 1.0f. A sequence of evenly spaced floating-point values from 0.0f to 1.0f are represented. For instance, a 2-bit UNORM represents 0.0f, 1/3, 2/3, and 1.0f.
In your example format DXGI_FORMAT_R8G8B8A8_UNORM there are 8 bits per channel, so 28 = 256 possible values (0-255).
Those will map to float values in the range 0-1 like the given example in the documentation:
Int Value Float Value 0 0 / 255 = 0.0f 1 1 / 255 ≈ 0.00392156862f 2 2 / 255 ≈ 0.00784313725f 3 3 / 255 ≈ 0.01176470588f ... ... 127 127 / 255 ≈ 0.49803921568f 128 128 / 255 ≈ 0.50196078431f ... ... 253 253 / 255 ≈ 0.99215686274f 254 254 / 255 ≈ 0.99607843137f 255 255 / 255 = 1.0f 
DXGI_FORMAT_R16G16B16A16_UINT for example can have a value from 0-65535 per channel, etc... \$\endgroup\$