Operating Systems

Segmentation is a Memory Management technique in which memory is divided into variable sized chunks which can be allocated to processes. Each chunk is called a segment. A table stores the information about all such segments and is called Global Descriptor Table (GDT). A GDT entry is called Global Descriptor. It comprise of :

To translate a logical address into a linear address, the processor does the following: # Uses the offset in the segment selector to locate the segment descriptor for the segment in the GDT or LDT and reads it into the processor. (This step is needed only when a new segment selector is loaded into a segment register.) # Examines the segment descriptor to check the access rights and range of the segment to insure that the segment is accessible and that the offset is within the limits of the segment. # Adds the base address of the segment from the segment descriptor to the offset to form a linear address. If paging is not used, the processor maps the linear address directly to a physical address (that is, the linear address goes out on the processor's address bus). If the linear address space is paged, a second level of address translation is used to translate the linear address into a physical address.

A segment selector is a 16-bit identifier for a segment. It does not point directly to the segment, but instead points to the segment descriptor that defines the segment. A segment selector contains the following items: ; Index ; : (Bits 3 through 15). Selects one of 8192 descriptors in the GDT or LDT. The processor multiplies the index value by 8 (the number of bytes in a segment descriptor) and adds the result to the base address of the GDT or LDT (from the GDTR or LDTR register, respectively). ; ;

TI (table indicator) flag ; : (Bit 2). Specifies the descriptor table to use: clearing this flag selects the GDT; setting this flag selects the current LDT. ;

Here are a few:

1. CCNA - Cisco
2. CCNP - Cisco
3. Network+ - CompTIA
4. Security+ - CompTia
5. MCSA - Microsoft (has many network elements)
6. MCITP - Microsoft (many network elements)
   

once the business has purchased inventory, those funds are not available for other uses. The business views this as an acceptable tradeoff because the inventory is an investment that will hopefully generate returns, but keeping the operating cycle short is still a goal for most businesses so they can keep their liquidity high.

Keeping inventory during a long operating cycle does not just tie up funds. Inventory must be stored and this can become costly, especially with items that require special handling, such as humidity controls or security. Furthermore, inventory can depreciate if it is kept in a store too long. In the case of perishable goods, it can even be rendered unsalable. Inventory must also be insured and managed by staff members who need to be paid, and this adds to overalloperating expenses.

There are cases where a long operating cycle in unavoidable. Wineries and distilleries, for example, keep inventory on hand for years before it is sold, because of the nature of the business. In these industries, the return on investment happens in the long term, rather than the short term. Such companies are usually structured in a way that allows them to borrow against existing inventory or land if funds are needed to finance short-term operations.

Operating cycles can fluctuate. During periods of economic stagnation, inventory tends to sit around longer, while periods of growth may be marked by more rapid turnover. Certain products can be consistent sellers that move in and out of inventory quickly. Others, like big ticket items, may be purchased less frequently. All of these issues must be accounted for when making decisions about ordering and pricing items for inventory.

Q.4 What is the implication of operating leverage for a firm.

Ans.

Operating leverage: Operating leverage is the extent to which a firm uses fixed costs in producing its goods or offering its services. Fixed costs includeadvertising expenses, administrative costs, equipment and technology, depreciation, and taxes, but not interest on debt, which is part of financial leverage. By using fixed production costs, a company can increase its profits. If a company has a large percentage of fixed