Is there default value for the registers in agal?

For registers such as Texture sampler registers,

if we upload one texture without alpha channel by uploadFromByteArray,and setTextureAt fs0,then

tex ft0, v0, fs0 <2d, linear, nomip>

What is the value for ft0.w?Does it have a default value 1.0?

For registers such as Attribute registers,

the same question is there for va0.w etc.