National Semiconductor ( NSM) posted a loss in the fiscal fourth quarter, reversing a profit a year ago, and the company's guidance had its shares under pressure Thursday afternoon. The analog semiconductor company reported revenue of $425.3 million for the fourth quarter, along with a loss of $4.4 million, or 2 cents a share. The fourth-quarter loss included $26.6 million of charges. Excluding the charges, National would have reported earnings of $22.2 million, or 12 cents a share. In the same quarter a year ago, National had revenue of $419.5 million, and a profit of $17.1 million, or 9 cents a share, including a tax refund of $11.5 million. Earnings would have been $5.6 million, or 3 cents a share, before the gain. On a sequential basis, fourth-quarter revenue increased 5% from third quarter. Gross margins rose to 44.6% from 42.7% in the third fiscal quarter. "Our business has improved," the company said in a press release. "We're on track with our plan to create higher returns faster for National's shareholders." National expects fiscal first-quarter revenue to be flat to down 4% from the fourth quarter, which the company said is consistent with historical patterns during the summer quarter. The company also believes gross margins will be flat to slightly lower. Operating expenses are expected to decrease. Analysts polled by Thomson First Call were looking for a profit of 9 cents in the latest quarter. Wall Street expects National to earn 11 cents a share in the first quarter, with revenue of $431.2 million. Shares of National were losing 95 cents, or 3.9%, to $23.73 in afternoon New York Stock Exchange trading.