The correct answer is the C/A code, which stands for Coarse/Acquisition code. This digital code is specifically designed for civilian use and is broadcast on the L1 frequency by GPS satellites. The C/A code is readily accessible by all standard GPS receivers and serves as one of the primary means for these devices to determine their position. It consists of a sequence of bits that makes it possible for receivers to identify and lock onto GPS signals, thereby calculating the pseudorange to the satellites.
The C/A code is essential for everyday applications, such as navigation for vehicles and smartphones, as it enables users to receive accurate location data without the need for specialized equipment. This accessibility allows a wide range of applications and services to utilize GPS technology effectively.
In contrast, the P code (Precise code) is used for military purposes and provides greater accuracy but is encrypted, which restricts its use to authorized users. The Y code is associated with a more advanced and precision capability, which also includes encrypted elements. Pseudorange, while a term related to measuring distances between a satellite and a receiver, does not refer to a specific digital broadcast code. Thus, the C/A code is the foundational code that ensures broad access to GPS functionality for civil users.