题目内容

案例分析题实体完整性约束指的是（），参照完整性约束指的是（）。参照完整性约束指的是（）。

A. 若关系R的外码是属性(或属性组)F，它与关系S的主码K相对应，则关系S的主码K的取值必须在关系R中属性(或属性组)F的取值范围内
B. 若关系R的外码是属性(或属性组)F，它与关系S的主码，K相对应，则关系R中属性(或属性组)F的取值必须在关系S的主码K的取值范围内
C. 若关系R的外码是属性(或属性组)F，它与关系S的主码K相对应，则对于R中每个记录在F上的值必须等于S中某个记录的主码值。
D. 若关系R的外码是属性(或属性组)F，它与关系S的主码K相对应，则对于R中每个记录在P上的值或者取空值(F的每个属性值均为空值)；或者等于S中某个记录的主码值。

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案例分析题（）是关系数据库的标准语言，它主要由（）和一些其它语言要素组成。它主要由（）和一些其它语言要素组成。

A. 数据定义语言，数据操纵语言和数据控制语言
B. 数据定义语言，数据操纵语言和数据说明语言
C. 数据定义语言，数据说明语言和数据控制语言
D. 数据说明语言，数据操纵语言和数据控制语言

案例分析题The UNIX operating system is made up of three parts; the kernel, the shell and the programs. The kernel of UNIX is the （） of the operating system: it allocates time and memory to programs and handles the filestore and communications in response to （） .The shell acts as an （） between the user and the kernel. When a user logs in, the （） program checks the username and password, and then starts another program called the shell. The shell is a command line （） (CLI). It interprets the commands the user types in and arranges for them to be carded out. The commands are themselves programs: when they terminate, the shell gives the user another prompt (% on our systems). The kernel of UNIX is the （） of the operating system.

A. hub
B. center
C. core
D. nucleus

As mentioned above, C imposes relatively few built - in ways of doing things on the program- mer. Some common tasks, such as manipulating (66) , (67) , and doing (68) (I/O), are performed by calling on library functions. Other tasks which you might want to do, such as creating or listing directories, or interacting with a mouse, or displaying windows or other (69) elements, or doing color graphics, are not defined by the C language at all. You can do these things from a C program, of course, but you will be calling on services which are peculiar to your programming environment (70) , processor, and operating system) and which are not defined by the C standard. Since this course is about portable C programming, it will also be steering clear of facilities not provided in all C environments. （70）处应选择（）

A. gatherer
B. translator
C. generator
D. compiler

案例分析题The UNIX operating system is made up of three parts; the kernel, the shell and the programs. The kernel of UNIX is the （） of the operating system: it allocates time and memory to programs and handles the filestore and communications in response to （） .The shell acts as an （） between the user and the kernel. When a user logs in, the （） program checks the username and password, and then starts another program called the shell. The shell is a command line （） (CLI). It interprets the commands the user types in and arranges for them to be carded out. The commands are themselves programs: when they terminate, the shell gives the user another prompt (% on our systems). it allocates time and memory to programs and handles the filestore and communications in response to （）

A. system commands
B. system calls
C. system transfer
D. system deliver