In other words, a "float" in C is usually single-precision, or 32-bits; and a "double" is usually double-precision, or 64 bits. You can see this by using sizeof(float) and sizeof(double); those values are usually 4 (8 bits * 4 bytes = 32 bits) and 8 (8 bits * 8 bytes = 64 bits). This should be the same on all platforms. You can check by using sizeof(float)/sizeof(double) on both platforms. If they're the same value, it's likely that the format is the same.
IEEE 754 specifies four formats for representing floating-point values: single-precision (32-bit), double-precision (64-bit), [...]. For example, the C programming language, which pre-dated IEEE 754, now allows but does not require IEEE arithmetic (the C float typically is used for IEEE single-precision and double uses IEEE double-precision).